Answer: UBOATS

AnswerCrossword Clue
UBOATSSubmerged threats of WW2
UBOATSW.W. II craft
UBOATSCorvettes' targets
UBOATSUnderwater "wolf pack"
UBOATSW.W. II wolf pack
UBOATSWorld War II vessels
UBOATSMaritime hazard in W. W. II
UBOATSWorld War marine menaces
UBOATSThreats to World War shipping
UBOATSW.W. II threats
UBOATSOld minelayers
UBOATSWWII "wolf pack"
UBOATSGerman military subs
UBOATSWWII ship sinkers
UBOATSSea raiders
UBOATSMaritime hazard in WWII
UBOATSWWII maritime hazard
UBOATSMaritime hazards in WWII
UBOATSAshcan targets
UBOATSSome WWII crafts
UBOATSDepth-charge targets
UBOATSDestroyer destroyers
UBOATSCommerce-raiding fleet
UBOATSWolf pack makeup
UBOATSThey hid beneath the surface
UBOATSBattle of the Atlantic craft
UBOATSW.W. II shipping worries
UBOATSWWII threats
UBOATSBattle of the Atlantic attackers
UBOATSWWII depth charge targets
UBOATSWWII fleet
UBOATSGerman subs
UBOATSDepth charge targets
UBOATSSubmerged threats of WWII
UBOATSWolf pack members
UBOATSWolf pack units
UBOATSWWI menaces
UBOATSWW II fleet
UBOATSEnemy submarines, once
UBOATSSome subs