Notes
The Time Mercenaries, a novel by Philip E. High.

Publication date unknown, but the ISBN and the presence of an advertisement for These Savage Futurians on the rear jacket flap suggest that it was published after April 1969, possibly in September 1969.

Blurb – Jacket Flap
There had been one war scare too many and so the human race had used genetic sorcery to delete the aggressive tendencies from its heredity. But now mankind was faced with an alien enemy so superior, so ruthless, that it was fight or be wiped out . . . and the humans could not fight. They couldn’t even give orders to their robots to produce weapons.

The only possibility was to call up and bring back to life a museum exhibit, the submarine Euphrates and its battle-trained crew. The ship had been sunk a thousand years before and had been preserved to show the decadence of violence – violence which was the only hope against an enemy to whom living space was all-important and human life was entirely superfluous.