 In mid 1971 I Corps, a critical area bordered by North Vietnam and Laos, was protected by ARVN infantry, three ARVN armored cavalry squadrons, and the US 1st Brigade, 5th Infantry Division (Mechanized), scheduled to leave the country in August.Analysis of terrain, the probable People's Army of Vietnam (PAVN) threat, and PAVN armored actions during Operation Lam Son 719 made it clear that armored units would continue to be needed in this area.Consequently the South Vietnamese Joint General Staff (JGS) authorized on 31 July 1971 the formation of the 20th Tank Regiment.