The Mercenaries: Mad Dogs and Englishmen by P. W. Storm

Michael "Mad Dog" Hertzog lived for soldiering—but he wasn't willing to die following the orders of bureaucrats and incompetents. Now he and his private army of warriors-for-hire are doing war Dog's way.

Hertzog's right hand man has vanished . . . along with $30 million of Mad Dog's money. The evidence says a trusted British merc has gone rogue, but there may be a different, more virulent form of treachery at work here. There are answers waiting aboard a train racing east from Moscow, carrying Russian gangsters, stolen Siberian diamonds, a shadow team of Iranian agents . . . and a pair of nuclear warheads. Suddenly the stakes have gotten perilously high for Mad Dog, his team, and the world . . . as time ticks rapidly away on a terrifying plot to bathe the Middle East in nuclear fire.