Trying to jog my memory about the book title and author of an old space opera book I read back in the day.
Story elements as best I can remember (pretty much spoilers):
- Aliens make contact with humanity. IIRC the aliens are pretty much human except some might have unusual hair color.
- There's a massive interstellar war going on between these first aliens and some other foe alien group about to overrun human space.
- The initial contact aliens are short of personnel but have plenty of ships to give humans for self defense.
- Humans end up mastering the use of these massive (spherical?) battleships to fight the oncoming enemy (no single person attack craft). They have to fuel them up with water (possibly obtained from comet mining).
- The foe aliens show up and humans put up a fight, but things go badly. The foe are far superior.
- The protagonist's ship uses a bold strategy: They get everyone into their ship's water tank in space suits and crash their ship into one of the enemy ships at maximum speed. Then they climb out, board the enemy ship and take over.
- It turns out the ship they hit was the enemy command ship, and they score a decisive victory.
- It also turns out that the "foe" are actually the aliens that contacted them initially. They apparently staged this war so that the rebellious youths of their planet would have something to do other than run amok at home. The ships they gave the humans to use were outdated models.
At least that's how I think the story went. I keep thinking the title was "Them", but even if that's right it's such a common word that my searches are not going well.
I probably read this in the late 1980s or early 1990s, but it may well date a decade or more earlier.
Any help in figuring this out is appreciated.