After the Soviet Union launched Sputnik 2, on November 3, 1957, then Secretary of Defense Neil H. McElroy directed the U.S. Army to use the Juno I and launch a satellite. On January 31, 1958, the U.S. Army launched the Explorer 1 satellite. With the launch of Sputnik 1 and 2 the previous concern, the right of satellite overflight, had become moot: those satellites were launched by an early version of the Soviet R-7 rocket, the basis of the USSR's early ICBMs, and definitely military, as well as roughly 40 times larger than the Vanguard launcher.