Despite the revamped effort at fighting the enemy on their own terms, U.S. operations remained insufficient at eliminating the tunnels completely. In 1967, General William Westmoreland tried to launch a larger assault on Củ Chi and the Iron Triangle. Called Operation Cedar Falls, it was similar to the previous Operation Crimp but was on a larger scale with 30,000 troops, instead of 8,000. On January 18, tunnel rats from the 1st Battalion, 5th Infantry Regiment, 25th Infantry Division uncovered the Viet Cong district headquarters of Củ Chi, containing half a million documents concerning all types of military strategy. Among the documents were maps of U.S. bases, detailed accounts of PLAF movement from Cambodia into Vietnam, lists of political sympathizers, and even plans for a failed assassination attempt on Robert McNamara.