 Starting on 5 January, blocking forces assumed their positions to south of the Iron Triangle along the Saigon River (the 25th Infantry Division and the 196th Infantry Brigade) and east of it (1st Infantry Division) to set up the anvil.On D-day, finally, elements of the 1st Infantry Division's 2d Brigade commenced the planned air assault on the village of Ben Suc.Ben Suc was the main pillar of the VC's dominance over the Iron Triangle.