What if Russia stayed out of both world wars?
Short answerBritain avoids Arctic and Persian supply routes in World War II and probably has no reason for the Dardanelles campaign in World War I, freeing ships and resources for other theaters.
NotesIf Germany also refrains from attacking Russia, Britain no longer has to sustain the Arctic convoys or the Persian supply corridor and could redirect resources toward Singapore. In World War I, removing the need to reach Russia through the Dardanelles could prevent Gallipoli and leave additional heavy ships available elsewhere, possibly including Jutland.