You will constantly lose deck hands from battles and must recruit more from the Tavern. You can recruit two deck hands for each crop unit. Upgrade your Tavern to recruit more deck hands.
How to enter Tavern:
a. At your home base, tap Tavern to recruit deck hands.
b. Tap Tavern when preparing for battle.
c. Tap the “+” to select how many deck hands you want to recruit.
The recruited Deck hands are automatically assigned to your officers. When your officers are missing deck hands from their ranks but the number is not yet at 0, your officers cannot take as much damage in battle. When you have 0 deck hands, you can no longer continue fighting.