By Christmas 1972, most U.S. troops were out of Vietnam. There were some pending issues, but the fighting was done.    President Nixon had two objectives: Get a peace accord signed and arrange for the release of POWs. Suddenly, North Vietnam began to play games with Secretary of State Henry Kissinger. They would argue about this and that to delay the accords.   It frustrated the U.S. side and President Nixon decided to send a message to North Vietnam. It was called Operation Linebacker II. We call it the Christmas bombing of 1972: President Nixon initiated the full-scale bombing campaign against North Vietnam on December 18, when the North Vietnamese -- who walked out of the peace talks in Paris -- refused an ultimatum from Nixon to return to the negotiating table.  During the 11 days of the operation, 700 B-52 sorties and more than 1,000 fighter-bomber sorties dropped an estimated 20,000 tons of bombs, mostly over the densely...(Read Full Post)