Why battleships briefly carried depth-charge throwers

What was the largest surface warship fitted with ship-launched depth charges?

Japanese battleships are identified as the likely answer; depth-charge experiments were once much more widespread than modern readers may expect.

Many navies experimented with depth charges on a wide range of ships after early wartime encounters with submarines. Japanese battleships are identified as the likely largest surface warships equipped with dedicated throwers rather than simple stern racks. The Royal Navy later retained helicopter-delivered depth charges for submarines sitting motionless near a monitored area. A stationary target can be awkward for a homing torpedo, while a helicopter that fixes its position can drop charges at the required depth and force it to move or be destroyed.