Doctrine assumes the Royal Navy will be locally outnumbered

The doctrine rested on tested weapons, a maritime empire dependent on commerce, and the need to cover widely separated theaters. Britain could be the world's strongest navy in aggregate while lacking a permanent third fleet for the Indian Ocean and Far East. The United States had yet to build equal strength under treaty parity, and British planners expected that any later American support would take time to enter a conflict. Forces in the Mediterranean or Far East might have to hold while locally outnumbered. Aviation's reconnaissance, range, night capability, and disruptive power offered ways to turn that local inferiority into a favorable engagement.