Crossing the T
Crossing the T is a tactic that dates back to the the earliest use of naval cannons. Sailing ships were long and relatively narrow to reduce total mass and reduce drag, so there was very little space to fit cannons in the bow of a ship of the line. The logical choice, therefore, was to place the majority of a ship's firepower in multiple decks along its sides (hence the term 'broadside').
"Crossing the T" refers to maneuvering such a ship ahead of and roughly perpendicular to an enemy ship's path, allowing the attacker to use it's full broadside firepower without exposing itself to much return fire from the target. While the target profile is harder to hit, the sheer volume of shots gives the ship "crossing the T" a greater chance of doing damage. This tactic became much more effective once battleships began to mount rotating turrets, making more of a ships guns capable of hitting the enemy.
The most spectacular uses of the tactic would be by the British Grand Fleet against the German High Seas Fleet at the battle of Jutland. At Jutland, the British fleet intercepted the German fleet. In one of the largest naval battles in history, the Germans ended up having their T crossed twice. The second time, hoping to cross the British T, the Germans wheeled their fleet around for a second pass at the British fleet, but were outmaneuvered.
This tactic was effective (to varying degrees) up until World War II, when carrier-based aircraft largely replaced ship-mounted cannons as the primary means of attacking enemy shipping. The last time this tactic was effectively used in battle was during the Battle of Leyte Gulf at Surigao Strait. The subsequent invention of long-range missiles and further advances in aircraft technology sealed this tactic's fate forever; it has not seen significant use for decades.
Crossing the T in Science Fiction
- In the Honor Harrington series of novels, crossing the T is an effective tactic due to the geometry of Honorverse Sidewalls.