Perry improvises a tactic which enables the CDF to win this first battle quickly.
This is soon followed by a number of battles with, among others, the bear-like Whaidians and the tiny Covandu.
The Skip Drive takes an object like a space ship, punches a hole in space, and places the object at its destination in a new, essentially identical universe.
There are limits on the skip drive due to the characters not knowing all there is to know about how it works.
The characters in Old Man's War have enhanced DNA and nanotechnology, giving them advantages in strength, speed, endurance, and situational awareness.
John Perry, a 75-year-old retired advertising writer, joins the Colonial Defense Forces who protect human interplanetary colonists.
By the end of this last engagement Perry begins to suffer psychological distress over killing the Liliputian Covandu and accepts that he has transformed both physically and mentally.
Now a veteran, Perry participates in the Battle for Coral.
Perry's quick thinking allows him and his fellow soldiers on a transport shuttle to escape the wreckage of the Modesto and make for the planet's surface, but they are shot down.
Everyone but Perry is killed in the crash; Perry is grievously wounded but survives thanks to his artificially enhanced body.