 After the first week of operations , additional battalion and brigade units were committed to the operation , so that between 6 and 24 May , a total of 90 @,@ 000 Allied troops ( including 33 U.S. maneuver battalions ) were conducting operations inside Cambodia . Due to increasing political and domestic turbulence in the U.S. , President Nixon issued a directive on 7 May limiting the distance and duration of U.S. operations to a depth of 30 kilometers ( 19 mi ) and setting a deadline of 30 June for the withdrawal of all U.S. forces to South Vietnam . 
