6 5 ▁before ▁author izing ▁a ▁major ▁bomb ing ▁campaign ▁of ▁North ▁Vietnam . ▁The ▁subsequent ▁eight - week ▁bomb ing ▁campaign ▁had ▁little ▁apparent ▁effect ▁on ▁the ▁overall ▁course ▁of ▁the ▁war . ▁In ▁a ▁campaign ▁known ▁as ▁Operation ▁Rol ling ▁Th under ▁the ▁U . S . ▁would ▁continue ▁to ▁bomb ▁North ▁Vietnam ▁until ▁late ▁ 1 9 6 8 , ▁dro pping ▁approximately ▁ 8 0 0 ▁tons ▁of ▁bomb s ▁over ▁three ▁and ▁a ▁half ▁years . ▁Operation ▁Rol ling ▁Th under ▁In ▁March , ▁Mc Ge orge ▁Bund y ▁began ▁to ▁ur ge ▁the ▁es cal ation ▁of ▁U . S . ▁of ▁ground ▁forces , ▁arg uing ▁that ▁American ▁air ▁operations ▁alone ▁would ▁not ▁stop ▁H ano i ' s ▁ag gression ▁against ▁the ▁South . ▁Johnson ▁respond ed ▁by ▁appro ving ▁an ▁increase ▁in ▁soldiers ▁station ed ▁in ▁Vietnam ▁and , ▁most ▁important ly , ▁a ▁change ▁in ▁mission ▁from ▁def ensive ▁to ▁off ensive ▁operations . ▁Even ▁so , ▁he ▁def i antly ▁continued ▁to ▁ins ist ▁that ▁this ▁was ▁not ▁to ▁be ▁public ly ▁represented ▁as ▁a ▁change ▁in ▁existing ▁policy . ▁▁ ▁In ▁late ▁July , ▁Secretary ▁of ▁Def ense ▁Mc N am ara ▁proposed ▁to ▁increase ▁the ▁number ▁of ▁U . S . ▁soldiers ▁in ▁Vietnam ▁from ▁ 7 5 , 0 0 0 ▁to ▁over ▁ 2 0 0 , 0 0 0 ▁in ▁order ▁to ▁conv ince ▁North ▁Vietnam ese ▁leader ▁Ho ▁Chi ▁Min h ▁to ▁seek ▁a ▁negoti ated