Laid down in 1911, launched in 1912, and commissioned in 1913, Seydlitz entered service at 26.5 knots just as British speed standards were rising. She was slower than HMS Queen Mary and only modestly faster than the Queen Elizabeth-class battleships as completed, while the discarded small-tube-boiler concept pointed toward an even faster British battleship. In this analysis, a battlecruiser needs roughly three knots of margin to control the range and pace of an engagement. Damage could therefore erase Seydlitz's ability to choose the range or escape, unlike Queen Mary facing Germany's roughly 21-knot dreadnoughts. The German choice to devote hull volume and weight to armor and subdivision improved survival in a battle-line role but directly reduced the speed that defined a battlecruiser's tactical freedom.
Chapter · 22:10-25:37
Seydlitz's shrinking speed advantage
At 26.5 knots, Seydlitz lacked the decisive speed margin a battlecruiser needed over contemporary British battlecruisers and emerging fast battleships.