Struma Pass
a cleft in the mountain chain which formerly constituted the frontier between Turkish Macedonia and Bulgaria, through which runs the River Struma, and which constituted one of the gateways into Bulgaria by which the Allied troops advanced into Bulgaria during their successful offensive, in September, 1918. World War. It was at this point that the Allies invaded Bulgaria proper, on September 25, 1918, as part of the general advance, begun a week before, which terminated in the complete collapse of the Bulgarian resistance, and proved the beginning of the end of the war as a whole.