 The North Vietnamese launched a wave of attacks in the late night hours of 30 January in the I and II Corps Tactical Zones of South Vietnam . This early attack did not lead to widespread defensive measures . When the main North Vietnamese operation began the next morning the offensive was countrywide and well coordinated , eventually more than 80 @,@ 000 North Vietnamese troops striking more than 100 towns and cities , including 36 of 44 provincial capitals , five of the six autonomous cities , 72 of 245 district towns , and the southern capital . The offensive was the largest military operation conducted by either side up to that point in the war . 
