For their surprise attack on Pearl Harbor, the Japanese used a mix of torpedoes and bombs, some of which were specially modified for the attack.
By December 1941, the Japanese had refined their “Type 91, Modification 2″ torpedo to be extremely reliable. But Pearl Harbor’s shallow 45-foot waters posed a problem: When a torpedo fell, it typically plunged at least 100 feet before rising to attack at depth.
After extensive testing, the Japanese attached wooden tail fins and slid wooden casings over the anti-roll tabs on the side of the torpedo.
Both additions – which increased surface area, increased buoyancy and broke loose on impact with the water – proved decisive.
Torpedo planes coordinated their attack with planes carrying Type 99 anti-ship bombs, which were converted artillery shells.
When dropped from great heights, the streamlined projectiles can pierce steel armor, penetrate a ship’s decks and explode.
One such bomb caused the massive fatal explosion aboard the USS Arizonakilling 1,177 soldiers within seconds.
To hit targets further inland, dive bombers carried the Type 98 general-purpose bomb, which wreaked havoc on airfields, structures, vehicles, and parked aircraft.
This story originally appeared on HistoryNet.com.