What does HP stand for?

HP stands for Health Points of a pertaining Officer in the game. This equates to the vitality of the pertaining officer. As the HP value goes higher (by upgrading or promoting), its relative toughness in battles (meaning the number of hits it could take from enemies), increases as well. HP value of officers is mainly beneficial and realized when taking part in Special Operation Levels, Special Secret Base Corps battles, and Counterattack. Hope this helps!

Health points. Once they reach zero your troop will die