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 populated area between Hanoi and Haiphong. 

President Nixon was vilified at home and abroad for ordering the “Christmas bombing,” but on December 28, the North Vietnamese did agree to return to the talks in Paris. When the negotiators met again in early January, they quickly arrived at a settlement. 

The Paris Peace Accords were signed on January 23 and a ceasefire went into effect five days later.

President Nixon was called every name on the book, from war criminal to Hitler to whatever else the left could come up with.  

However, the bombing worked and the accord was signed ending the war and recognizing South Vietnam.   

Also, a timetable for releasing POWs was accepted. They started coming home in March.

There are two lessons here for President Obama:

1) American power works. It delivers a message when one must be delivered.

2) A bold president is respected by our adversaries. As I  heard one POW say in a radio interview, he knew that he was going home when those B-52s hit Hanoi very hard over Christmas.

There are limits to air power and military activities. However, it can work if you have a president who understands that he is the leader of the free world and commander in chief of the greatest armed forces in history.

P.S. You can listen to my show (Canto Talk) and follow me on Twitter.