Jackie Fisher was appointed commander in chief of the British Royal Navy in the years before WWI. Aircraft had not been invented yet. Fisher saw his problem as finding the German Navy at sea and engaging it with the larger Royal Navy. The Germans (and everybody else) would have a screen of cruisers around the battle fleet. Cruisers could easily sink contemporary destroyers so having destroyers search for the enemy would just get a lot of destroyers sunk. Fisher demanded a special purpose vessel, the battle cruiser, to go looking for the enemy. The battle cruiser had to be fast, which called for a big ship, and heavily armed so it could blow enemy cruisers out of its way. The result was a fine looking vessel, as big and handsome as a battle ship, but lacking a battleship’s armor. The officers appointed to command the battle cruisers though they had command of a battleship and acted accordingly.
At the climatic WWI battle of Jutland, the British battle cruisers were commanded by flamboyant Admiral Beatty. Beatty took his fleet of four battle cruisers out into the North Sea and located the German battle fleet. At this time, Beatty should have broken off the action, radioed German position course and speed to British Grand Fleet and then run for it.
Instead, Beatty engaged the German battle ship fleet and had three of his four battle cruisers were sunk by German fire. “There seems to be something wrong with our ships today” said Beatty at the time. Beatty didn’t even bother to radio the German’s position, course and speed back to Grand Fleet.
Fortunately for the British, Grand Fleet was commanded by canny old Admiral Jellico. Jellico looked at the weather, the tides, and what Intel he had, and figured out just where the German fleet was going. He got it right, and Grand Fleet was able to find the Germans, and cross the German’s Tee, the decisive maneuver in battle ship actions.
HMS Hood was laid down as a battle cruiser during WWI but was not finished and launched until the war was over. After the destruction of three battle cruisers at Jutland, the British beefed up the armor on Hood. But they treated her as a battle ship even though her armor was only 6 inches instead of the 12 inches considered proper for real battleships. Twenty years later Hood was send out to stop Bismarck. Bismarck scored a single hit on Hood’s deck, the shell went right thru and exploded and Hood sank in minutes. The last of the battle cruisers.