What was 'Tet offensive'?

The North Vietnamese lose the battles, but win the war. That's the shorthand answer but it's incomplete and misleading. The Tet Offensive of 1968, though it received a lot of attention, led directly to nothing. Four years later, the Paris Peace Accords signed on January 27, 1973, ended the fighting between the North and the South and the USA. It came immediately after Nixon was reelected and sworn in again as President for what was thought to be four more years. But a year and a half later, after Nixon was forced from office and replaced by Ford, the US Congress and Ford abandoned the South, leading to the military takeover by the North. That was the break-through the North needed. The South, without assitance from the USA, could not contend with the North, with assistance from the USSR and China. Tet, which the North lost, was neither a necessary nor a sufficient cause of the victory by the north. A change in the US government is what was required, and that change was not even an indirect result of Tet.