Who had the most submarines during world war 2?

Germany was the only combatant of WWII without an aircraft carrier (they never finished their only carrier & if one doesn't count Italy & the Soviets). Consequently they had a weak navy. This being the case, the DKM had to concentrate on a strategy called "Guerre de Course", meaning fighting a sea war against merchant ships, sometimes referred to as "Commerce raiding." The best tool for this job was submarines. Germany had the most subs.