Countdown trilogy by Tom Kratman

three books not linked as a serie on amazon :

Countdown: The Liberators, Countdown: M Day, and Countdown: H Hour

BACK IN ACTION

Old soldiers never die… except inside, when they lack a reason to live. Old soldier Wes Stauer is dying inside, from sheer lack of purpose.

And then comes the knock on the door: ”Our leader’s son and heir has been kidnapped. We don’t know where he is. We need you to get him back for us. The people who have him are numerous, warlike, and well armed. But money is no object.”

And then old soldiers-sailors and airmen, too-stop fading away and come back into sharp focus.