On 30 January 1968 the North Vietnamese forces and Viet Cong launched the Tet offensive across South Vietnam, marking a significant change from the guerrilla tactics used throughout the war so far. The offensive coincided with the Tet celebration, which marks the arrival of spring in the Vietnamese calendar. This holiday had typically seen truces in previous years, so the 1968 Tet offensive came as a surprise. An increase in Communist attacks near the borders towards the end of 1967 had raised suspicions of a diversion, so large numbers of American troops were recalled to the main cities as a precaution. Saigon was the main focus of the Communist attack, which struck cities all over South Vietnam, but after the initial surprise, the Communist forces were contained. The Tet offensive, which involved over 70,000 Communist troops, did not achieve its goal of starting a general uprising but did significantly reduce morale amongst American troops and civilians.