Mr. Justice Stewart
delivered the opinion of the Court.
Appellee Robert C. Ballard is a lieutenant in the United States Navy. After more than nine years of active service as a commissioned officer, he failed, for a second time, to be selected for promotion to the grade of lieutenant commander, and was therefore subject to mandatory discharge under 10 U. S. C. § 6382 (a). He brought suit in federal court claiming that if he had been a woman officer, he would have been subject to a different separation statute, 10 U. S. C. § 6401, under which he would have been entitled to 13 years of commissioned service before a mandatory discharge for want of promotion. He claimed that the application of § 6382 to him, when compared with the treatment of women officers subject to § 6401, was an unconstitutional discrimination based on sex in violation of the Due Process Clause of the Fifth Amendment.
The District Judge issued a temporary restraining order prohibiting Ballard’s discharge. Subsequently, a three-judge District Court was convened to hear the claim pursuant to 28 U. S. C. §§ 2282, 2284. After hearings upon motions by the Government defendants, that court issued a preliminary injunction against Ballard’s discharge. 350 F. Supp. 167. Thereafter, the case came before the three-judge court for decision on the merits. Relying upon Frontiero v. Richardson, 411 U. S. 677, and concluding that the challenged mandatory-discharge provisions are supported solely by considerations of fiscal and administrative policy, the court held that § 6382 is unconstitutional because the 13-year tenure provision of § 6401 discriminates in favor of women without sufficient justification. 360 F. Supp. 643. Accordingly, the court enjoined the Navy from discharging Ballard for failure to be promoted to the grade of lieutenant commander before the expiration of 13 years of commissioned service. Id., at 648. We noted probable jurisdiction of this appeal from that injunctive order. 415 U. S. 912. See 28 U. S. C. § 1253.
I
At the base of the system governing the promotion and attrition of male line officers in the Navy is a congressional designation of the authorized number of the Navy’s enlisted personnel, 10 U. S. C. § 5401, and a correlative limitation upon the number of active line officers as a percentage of that figure. § 5403. Congress has also established the ratio of distribution of line officers in the several grades above lieutenant in fixed proportions to the total number of line officers. §§ 5442, 5447 (a).
The Secretary of the Navy is required periodically to convene selection boards to consider and recommend for promotion male fine officers in each of the separate ranks, § 5701, and must provide the boards so convened with the number of male line officers that may be recommended for promotion to the next higher grade. § 5756. Eligible officers are then recommended for promotion by the selection boards, based upon merit, and are placed on a promotion list and promoted in due course as vacancies occur in the higher ranks. § 5769. Because the number of lieutenant commanders is set by statute, the number of lieutenants, like Ballard, who may be recommended for promotion and placed on a promotion list in any year depends upon the number of vacancies existing and estimated for the coming year in the rank of lieutenant commander. § 5756.
Wholly separate promotion lines are established for the various categories of officers. Thus, in addition to the selection boards that are convened to review the promotion of male line officers, different selection boards are convened to recommend for promotion staff corps officers (except for women officers appointed under § 5590), § 5702, male officers in the Marine Corps, § 5703, women line officers, § 5704 (a), and women staff officers who are appointed under § 5590. § 5704 (b). The convening of these separate selection boards permits naval officers within each category to be considered for promotion in comparison with other officers with similar opportunities and experience.
Because the Navy has a pyramidal organizational structure, fewer officers are needed at each higher rank than are needed in the rank below. In the absence of some mandatory attrition of naval officers, the result would be stagnation of promotion of younger officers and disincentive to naval service. If the officers who failed to be promoted remained in the service, the promotion of younger officers through the ranks would be retarded. Accordingly, a basic “up or out” philosophy was developed to maintain effective leadership by heightening • competition for the higher ranks while providing junior officers with incentive and opportunity for promotion. It is for this reason, and not merely because of administrative or fiscal policy considerations, that § 6382 (a) requires that lieutenants be discharged when they are “considered as having failed of selection for promotion to the grade of lieutenant commander ... for the second time.” Similar selection-out rules apply to officers in different ranks who are twice passed over for promotion.
The phrase “failed of selection for promotion” in § 6382 (a) is a statutory term of art. It does not embrace all eligible officers who have been considered and not selected for promotion. Before an officer is considered to have failed of selection for the first time, he must have been placed within a “promotion zone” established by the Secretary of the Navy. The Secretary each year establishes “promotion zones” of officers who will either be selected for promotion to the next higher grade or who will be considered to have failed of selection for promotion for the first time. See §§ 5764, 5776. The number of officers in the zones, established for each grade, is set at a level to ensure a flow of promotions consistent with the appropriate terms of service in each grade, see § 5768, and to provide opportunity for promotion of others in succeeding years. The number of officers within each zone is thus based on “a consideration of the number of vacancies estimated for the next higher grade in each of the next five years, the number of officers who will be eligible for selection in each of those years, and the terms of service that those officers will have completed.” § 5764 (a).
Section 6401 is the mandatory-attrition provision that applies to women officers appointed under § 5590, including all women line officers and most women officers in the Staff Corps. It provides for mandatory discharge of a woman officer appointed under § 5590 when she “is not on a promotion list” and “has completed 13 years of active commissioned service in the Navy.” § 6401. Section 6401 was initially intended approximately to equate the length of service of women officers before mandatory discharge for want of promotion with that of male lieutenants discharged under § 6382 (a). Subsequently, however, Congress specifically recognized that the provisions of § 6401 would probably result in longer tenure for women lieutenants than for male lieutenants under § 6382. When it enacted legislation eliminating many of the former restrictions on women officers’ participation in the naval service in 1967, Congress expressly left undisturbed the 13-year tenure provision of § 6401. And both the House and the Senate Reports observed that the attrition provisions governing women line officers would parallel “present provisions with respect to male officers except that the discharge of male officers probably occurs about 2 years earlier.” S. Rep. No. 676, 90th Cong., 1st Sess., 12; H. R. Rep. No. 216, 90th Cong., 1st Sess., 17 (emphasis added).
II
It is against this background that we must decide whether, agreeably to the Due Process Clause of the Fifth Amendment, the Congress may accord to women naval officers a 13-year tenure of commissioned service under § 6401 before mandatory discharge for want of promotion, while requiring under § 6382 (a) the mandatory discharge of male lieutenants who have been twice passed over for promotion but who, like Ballard, may have had less than 13 years of commissioned service. In arguing that Congress has acted unconstitutionally, appellee relies primarily upon the Court’s recent decisions in Frontiero v. Richardson, 411 U. S. 677, and Reed v. Reed, 404 U. S. 71.
In Frontiero the Court was concerned with “the right of a female member of the uniformed services to claim her spouse as a 'dependent’ for the purposes of obtaining increased quarters allowances and medical and dental benefits under 37 U. S. C. §§ 401, 403, and 10 U. S. C. §§ 1072, 1076, on an equal footing with male members.” 411 U. S., at 678. Under the governing statutes, a serviceman could automatically claim his spouse as a “dependent,” but a servicewoman’s male spouse was not considered to be a “dependent” unless he was shown in fact to be dependent upon his wife for more than one-half of his support. The challenged classification was based exclusively on gender, and the Government conceded that the different treatment of men and women service members was based solely upon considerations of administrative convenience. The Court found this disparity of treatment constitutionally invalid. In the words of the plurality opinion:
“[A]ny statutory scheme which draws a sharp line between the sexes, solely for the purpose of achieving administrative convenience, necessarily commands 'dissimilar treatment for men and women who are . . . similarly situated,’ and therefore involves the 'very kind of arbitrary legislative choice forbidden by the [Constitution] . . . .’ Reed v. Reed, 404 U. S., at 77, 76. We therefore conclude that, by according differential treatment to male and female members of the uniformed services for the sole purpose of achieving administrative convenience, the challenged statutes violate the Due Process Clause of the Fifth Amendment insofar as they require a female member to prove the dependency of her husband.” Id., at 690-691.
The case of Reed v. Reed, supra, involved quite similar considerations. In that case the Court considered the constitutionality of an Idaho probate code provision that, in establishing who would administer a decedent’s estate, gave a “mandatory” preference to men over women when they were in the same degree of relationship to the decedent. The Idaho law permitted no consideration of the individual qualifications of particular men or women as potential administrators, but simply preferred males in order to reduce probate expenses by eliminating contests over the relative qualifications of men and women otherwise similarly situated. The Court held that “[b]y providing dissimilar treatment for men and women who are thus similarly situated, the challenged section violates the Equal Protection Clause.” 404 U. S., at 77.
In both Reed and Frontiero the challenged classifications based on sex were premised on overbroad generalizations that could not be tolerated under the Constitution. In Reed, the assumption underlying the Idaho statute was that men would generally be better estate administrators than women. In Frontiero, the assumption underlying the Federal Armed Services benefit statutes was that female spouses of servicemen would normally be dependent upon their husbands, while male spouses of servicewomen would not.
In contrast, the different treatment of men and women naval officers under §§ 6382 and 6401 reflects, not archaic and overbroad generalizations, but, instead, the demonstrable fact that male and female line officers in the Navy-are not similarly situated with respect to opportunities for professional service. Appellee has not challenged the current restrictions on women officers’ participation in combat and in most sea duty. Specifically, “women may not be assigned to duty in aircraft that are engaged in combat missions nor may they be assigned to duty on vessels of the Navy other than hospital ships and transports.” 10 U. S. C. § 6015. Thus, in competing for promotion, female lieutenants will not generally have compiled records of seagoing service comparable to those of male lieutenants. In enacting and retaining § 6401, Congress may thus quite rationally have believed that women line officers had less opportunity for promotion than did their male counterparts, and that a longer period of tenure for women officers would, therefore, be consistent with the goal to provide women officers with “fair and equitable career advancement programs.” H. R. Rep. No. 216, supra, at 5. Cf. Kahn v. Shevin, 416 U. S. 351.
The complete rationality of this legislative classification is underscored by the fact that in corps where male and female lieutenants are similarly situated, Congress has not differentiated between them with respect to tenure. Thus women staff officers not appointed under § 5590 are subject to the same mandatory attrition rule of § 6382 (a) as are male officers. These include officers in the Medical, Dental, Judge Advocate General’s, and Medical Service Corps. See 10 U. S. C. §§ 5574, 5578, 5578a, 5579. Conversely, active male lieutenants who are members of the Nurse Corps, like female lieutenants in that Corps, are within the ambit of 10 U. S. C. § 6396 (c), which contains a 13-year tenure provision like § 6401.
In both Reed and Frontiero the reason asserted to justify the challenged gender-based classifications was administrative convenience, and that alone. Here, on the contrary, the operation of the statutes in question results in a flow of promotions commensurate with the Navy’s current needs and serves to motivate qualified commissioned officers to so conduct themselves that they may realistically look forward to higher levels of command. This Court has recognized that “it is the primary business of armies and navies to fight or be ready to fight wars should the occasion arise.” Toth v. Quarles, 350 U. S. 11, 17. See also Orloff v. Willoughby, 345 U. S. 83, 94. The responsibility for determining how best our Armed Forces shall attend to that business rests with Congress, see U. S. Const., Art. I, § 8, els. 12-14, and with the President. See U. S. Const., Art. II, § 2, cl. 1. We cannot say that, in exercising its broad constitutional power here, Congress has violated the Due Process Clause of the Fifth Amendment.
The judgment is reversed.
Title 10 U. S. C. §6382 provides:
“(a) Each officer on the active list of the Navy serving in the grade of lieutenant, except an officer in the Nurse Corps, and each officer on the active list of the Marine Corps serving in the grade of captain shall be honorably discharged on June 30 of the fiscal year in which he is considered as having failed of selection for promotion to the grade of lieutenant commander or major for the second time. However, if he so requests, he may be honorably discharged at any time during that fiscal year.
“(d) This section does not apply to women officers appointed under section 5590 of this title or to officers designated for limited duty.”
Ballard’s scheduled discharge carried with it an entitlement to a “lump-sum” severance payment of approximately $15,000, 10 U. S. C. ■ § 6382 (c), but would have terminated Ballard’s total service time (including seven years of enlisted service) short of the 20 years of service necessary for substantially greater retirement benefits.
Title 10 U. S. C. §6401 (a) provides:
“Each woman officer on the active list of the Navy, appointed under section 5590' of this title, who holds a permanent appointment in the grade of lieutenant and each woman officer on the active list of the Marine Corps who holds a permanent appointment in the grade of captain shall be honorably discharged on June 30 of the fiscal year in which—
“(1) she is not on a promotion list; and
“(2) she has completed 13 years of active commissioned service in the Navy or in the Marine Corps.
“However, if she so requests, she may be honorably discharged at any time during that fiscal year.”
The Fifth Amendment to the Constitution of the United States provides in pertinent part that no person shall “be deprived of life, liberty, or property, without due process of law.” Although it contains no Equal Protection Clause as does the Fourteenth Amendment, the Fifth Amendment’s Due Process Clause prohibits the Federal Government from engaging in discrimination that is “so unjustifiable as to be violative of due process.” Bolling v. Sharpe, 347 U. S. 497, 499. See also Schneider v. Rusk, 377 U. S. 163, 168.
Similarly, the authorized strength of the Supply Corps and the Civil Engineers Corps is established in set proportions to the authorized number of line officers. 10 U. S. C. § 5404 (a). More complicated formulas set the bounds for the numbers of staff officers in ■ other corps. E. g., § 5404 (b).
See S. Rep. No. 2120, 75th Cong., 3d Sess., 4. Parts of the Officer Personnel Act of 1947 that affected naval officers were codified in 10 U. S. C. § 5401 et seq., by the Act of Aug. 10, 1956, 70A Stat. 297. Title 10 U. S. C. § 6382 (a) is a codification of § 312 (h) of the Officer Personnel Act of 1947, 61 Stat. 860, and that section was based, in turn, on § 12 (c) of the Act of June 23, 1938, 52 Stat. 949.
Title 10 U. S. C. § 6382 (b) calls for the mandatory, discharge of lieutenants (junior grade) who twice fail to be selected for promotion to the grade of lieutenant. In the grades above lieutenant, statutory provisions require the mandatory retirement, instead of discharge, of officers twice passed over for promotion. 10 U. S. C. • §§ 6376, 6379, 6380.
Section 6401 does not apply to women officers, appointed pursuant to 10 U. S. C. §§ 5574, 5578, 5578a, and 5579, who are in the Medical, Dental, Judge Advocate General’s, and Medical Service Corps. These women staff officers are, like male officers, subject to §6382 (a).
The reason for the “not on a promotion list” language of § 6401, as contrasted with the “failed of selection” language of §6382 (a), is in part historical. Section 6401 was enacted as §207 (j) of the Women's Armed Services Integration Act of 1948, 62 Stat. 368. The “promotion zone” system was not established for women appointed under § 5590 until 1967. Pub. L. 90-130, 81 Stat. 374 (1967). See § 5764(d).
See Hearings on S. 1527 before the Senate Committee on Armed Services (subsequently S. 1641), 80th Cong., 1st Sess., 39. Although the statutory eligibility periods for promotion through the ranks to lieutenant commander is somewhat shorter, § 5751 (b), the normal time in service as an ensign, lieutenant (junior grade), and lieutenant is 12 years under peacetime conditions. § 5768 (a). Accordingly, a male line officer who had achieved the rank of lieutenant would typically have completed 12 years of service before being considered for the rank of lieutenant commander, and would have completed 13 years of service before being passed over twice for promotion to the grade of lieutenant commander.
See Pub. L. 90-130, 81 Stat. 374 (1967). This Act repealed numerical and percentage restrictions on women officers in certain grades, removed restrictions on permanent appointment of women officers to the rank of captain, and authorized women officers under certain circumstances to be eligible for flag rank. Congress also established a “promotion zone” system for women officers and indicated that the promotion and attrition of female officers were generally to correspond to the treatment of male officers. S. Rep. No. 676, 90th Cong., 1st Sess., 2.
According to the brief of the Solicitor General, the tenure differential has since been increased by the removal of time-in-grade restrictions and accelerated promotions resulting from the Vietnam conflict. See Exec. Order No. 11437, Dec. 2, 1968, 3 CFR 754 (1966-1970 Comp.). Thus in recent years the discharge of male officers under § 6382 (a) may have occurred about four years earlier than the discharge of women officers under § 6401, instead of the two years’ ■difference acknowledged by Congress in 1967.
The dissenting opinion argues that, in retaining § 6401 in 1967, Congress may not have intended to give a longer tenure to women line officers than to their male counterparts, because “it is certainly plausible to conclude that Congress continued to believe, as it had in 1948, that the separation provisions for men and women would, given the opportunity to work properly, result in equal average tenure for both sexes.” Post, at 517. This conclusion cannot, however, be reconciled with Congress’ recognition that mandatory retirement provisions for women line officers “parallel present provisions with respect to male officers except that the discharge of male officers probably occurs about 2 years earlier.” S. Rep. No. 676, supra, at 12; H. R. Rep. No. 216, 90th Cong., 1st Sess., 17 (emphasis added). Alternatively, the dissent seems to imply that the “anomalous” retention in 1967 of the 13-year tenure provision of § 6401 may have resulted from congressional inadvertence. Post, at 514-515. But this view cannot be squared with the legislative history either. A major factor prompting the 1967 amendments was Congress’ express concern that unless restrictions on promotions of women naval officers were lifted, the operation of § 6401 would cause excessive forced retirement of women lieutenants. In discussing the problem, the House Report explicitly described the 13-year provision:
“A particularly severe problem of promotion stagnation exists among WAVE officers in the Navy. The present grade limitations on promotion of WAVE officers to the grades of commander-lieutenant commander have so reduced the vacancies that the Navy will be forced to discharge most regular WAVE lieutenants when they reach their 13th year of service if r.elief is not provided.
“Present law (sec. 6401, title 10, United States Code) provides that women officers on the active list of the Navy in the grade of lieutenant must be discharged on June 30 of the fiscal year in which they complete 13 years of active commissioned service if not on a promotion list that year. The Navy estimates that without legislative relief, the attrition among women line lieutenants will average 50 percent or more over the next 5 years. The Navy considers such heavy attrition unacceptable.” H. R. Rep. No. 216, supra, at 6.
It is thus clear that Congress in 1967 intentionally retained the 13-year tenure provision of § 6401, and did so with specific knowledge that it gave women line officers a longer tenure than their male .counterparts.
We observe that because of the restrictions that were removed from women officers’ participation in naval service in 1967, see Act of Nov. 8, 1967, 81 Stat. 374; S. Rep. No. 676, 90th Cong., 1st Sess., more opportunity has become available for women officers. We are told by the Solicitor General that since 1967, the Secretary of the Navy has implemented a program for acceleration of women officers’ promotion and that today women are being considered for promotion within the same time periods as are men. Apparently believing that the need for a tenure differential has subsided, the Department of Defense has submitted a bill to Congress that would substitute for § 6401 the same rule that governs male lieutenants. See §§ 2 (5) and 4(18)(L) of H. R. 12405 (93d Cong., 2d Sess.), which contains a new provision as a proposed replacement of both § 6382 and § 6401. These developments no more than reinforce the view that it is for Congress, and not for the courts, to decide when the policy goals sought to be served by § 6401 are no longer necessary to the Navy’s officer promotion and attrition programs.