Carpet bombings of Laos, helping Nixon interfere with negotiations in Paris to end the war, looking the other way while Pakistan massacred people in Bangladesh, supporting Pinochet, etc.
That was past; then came the deal to an armistice to end the Vietnam War (though then after the armistice NVA and VC continued the war and South Vietnam collapsed). The point of that prize was not that there had been war, it was that the parties had signed to end hostilities.
In 2009, the peace prize really was quite strange in my opinion: Obama had achieved rather little except winning an election campaign (becoming the U.S. president the same year) on promises that undoubtedly sounded good to the Committee (but which later on were not kept very well or quickly).
The Obama prize was like giving a gold medal to a runner just because it will run some races and he tells you he wants to win . Nobody could understand it , it's still a mystery the reason behind it.
There are other examples where the Nobel prize has been given to someone who previously intensified the conflict, but then worked for peace. Menachem Begin and Anwar Sadat in 1978, for instance.
In 2009, the peace prize really was quite strange in my opinion: Obama had achieved rather little except winning an election campaign (becoming the U.S. president the same year) on promises that undoubtedly sounded good to the Committee (but which later on were not kept very well or quickly).