Coal quality behind the published performance

The class's 25-knot top speed and 2,460-nautical-mile range at 10 knots depended on a full load of suitable coal. Britain could draw on high-quality Welsh and Canadian coal, while German ships had been tested and operated early in their careers with better coal imported from Britain. Once wartime supply cut off that source, lower-quality domestic coal reduced attainable performance. The comparison with Second World War aviation fuel extends the point: fuel quality can change engine output and maintenance needs. Access to oil also appears as a design variable. More direct access to North American or Arabian oil might have encouraged earlier oil firing and turbine adoption, with consequences for hull layout. Logistics, infrastructure, and fuel access were part of tactical capability.