(hb; 1943: novella)
Originally published as a serial (called Fury) under the pen name Lawrence O'Donnell, this is a pure blast of action, with plenty of bobby pin twists.
The plot: Brian Scott, a Free Companion mercenary whose regiment (the Doones Brigade) protects the Montana Keep (an undersea Venusian city surrounded by an "impervium dome") is called into action, when the neighboring Virginia Keep hires another Free Company to attack the Montana Keep. This time, it's a different mission for Scott: a veteran, he's thinking about quitting the mercenary life, and joining the civilians (scientists and rich folk) -- who tolerate, but do not fully appreciate the Free Companions. There's also the matter of who he wants to spend his future with: Jeana, his longtime, loving Free Companion wife; or Ilene Kane, a younger, lively member of the Keep's elite.
Thrilling old-school science fiction tale. Worth your time, this.
A loosely-connected sequel, Destination: Infinity, followed "a year or two later" (according to David Drake, in his "Introduction" to the novella). David Drake wrote another novella, set in the same milieu, in 1991, titled The Jungle (which also contains Kuttner's source novella, Clash By Night).