However, the number of defenders in the Iron Triangle area was thought to be over 10,000. The offensive failed to destroy the NLF's headquarters or to capture any high-ranking officers and so it had little effect toward Hanoi's plan. Both search-and-destroy and clear-and-hold missions stretched into the third phase, which began in 1968. The number of missions mounted, especially after the US was hit by General Võ Nguyên Giáp's Tet offensive in 1968. As the war grew more aggressive, so did the missions, and search-and-destroy and clear-and-secure operations became merged.