This is an older story that I'd like to revisit but can't think of the title. The only scene/chapter I remember is toward the end of the book and the hero, who has time traveled back, has created his own private army. When the Cuban Missile Crisis happens he sends his army, who look like Stormtroopers, there to stop the Soviets. The Russian troops are shocked at how advice the private army is. A close woman friend of the hero's is killed while piloting a helicopter.
It is not much to go on but does this sound familiar to anyone?