Mackensen, Ersatz Yorck, and Germany's battlecruiser problem

Mackensen and Ersatz Yorck sit on a spectrum where increasing armament and protection bring the battlecruiser progressively closer to the battleship. Their roughly 27-28-knot speeds were too close to the proposed 26-knot L20 battle line to secure the decisive mobility advantage a battlecruiser needed. They also could not reliably outrun British battlecruisers or replace heavily armed battleships in a fleet action. Because Germany devoted scarce yards, engines, material, and design effort to both types, the projects illustrate a force-structure problem: copying British categories displaced investment from the faster battle line Germany's circumstances arguably required. Germany's ocean-liner industry offered relevant high-speed engineering experience that could have reinforced a fast-battleship programme. Zeppelin reconnaissance also weakened the case for consuming capital-ship yards and resources merely to obtain scouting information.