Short answers, pulled from the story.
The Tet Offensive began on the 31st of January 1968 as a massive military campaign launched by North Vietnamese forces against South Vietnam. It involved coordinated attacks across numerous cities including Huế and Saigon to break allied defensive lines.
Communist Party First Secretary Lê Duẩn and his ally Lê Đức Thọ led the militant faction that demanded military reunification without negotiations. This group opposed the moderate faction led by Trường Chinh and Võ Nguyên Giáp who favored economic stability and peaceful coexistence with the Soviet Union.
More than 5,800 civilians lost their lives during the battle while 116,000 were left homeless out of an original population of 140,000. The fighting lasted 25 days from the 31st of January until mid-February 1968 and resulted in the destruction of forty to fifty percent of the city.
Allied intelligence estimated enemy probable course of action based upon capabilities rather than intentions which made them believe communists could not launch such an ambitious enterprise. A MACV intelligence analyst stated that if they had gotten the whole battle plan it would not have been believed or credible to them.
A 19-man sapper team attacked the US Embassy at 02:45 on the 31st of January by blowing a hole in the surrounding wall and charging through. The attackers occupied the chancery grounds until all were killed or captured by U.S. reinforcements landed on the roof six hours later with loss of five U.S. personnel.