The Forward class's 25 knots made sense beside 18-knot pre-dreadnoughts, giving the scouts a seven-knot margin. Dreadnought could sustain 21 knots, compressing that advantage and forcing destroyers and cruisers toward higher speeds. A scout had to do more than match the battle line: it had to move ahead, investigate, and return to report. Preserving the earlier margin therefore required roughly 28 or 29 knots. A three-knot gain in battleship speed could thus make a recently built cruiser unsuitable for its original role.
Notable Point · 36:41-39:07
Why Dreadnought's three-knot gain raised scout speed requirements
A three-knot increase in battle-fleet speed demanded a still larger increase from cruisers that had to scout ahead and return.