Watching the war films in reverse, Billy Pilgrim sees war as restorative and peaceful. The film's action, going backwards, becomes truly inverted. Instead of planes shooting each other they suck bullets out of one another. Instead of dropping bombs to destroy cities, planes suck the bombs into their cargo chambers and make the cities safe. 

The bombers opened their bomb bay doors, exerted a miraculous magnetism which shrunk the fires, gathered them into cylindrical steel containers, and lifted the containers into the bellies of the planes.… The steel cylinders were taken from the racks and shipped back to the United States of America, where factories were operating night and day, dismantling the cylinders, separating the dangerous contents into minerals … [which] were then shipped to specialists in remote areas. It was their business to put them into the ground, to hide them cleverly, so they would never hurt anybody ever again.

What happens when Billy sees the movie going backwards?

The movie begins with the explosion of the bomb.  But as the movie plays backward, Billy sees the bomb coming back together, reentering the plane, returning the factory where it was made lovingly, and returning to its natural state.  The whole scene makes Billy think of Adam and Eve.  In other words, the movie ends with creation instead of destruction, birth rather than death, purity rather than corruption.