The introduction of convoys for the protection of merchant shipping, which began on a large scale during the middle of 1917, is generally regarded as one of the major turning points of World War I. Relevant to this was the failure of the German submarine campaign to end the war in 1917, or even to improve significantly Germany's position-one of the most important factors in sealing the fate of the Central Powers.
McKillip, Robert W.H.
"Undermining Technology by Strategy: Resolving the TradeProtection Dilemma of 1917,"
Naval War College Review: Vol. 44
, Article 3.
Available at: http://digital-commons.usnwc.edu/nwc-review/vol44/iss3/3