The presence of three Allied navies in the Mediterranean made any measures of their co-ordination and common doctrine extraordinarily difficult. The Mediterranean was divided into eleven zones, of which the British naval authorities were responsible for four, the French for four, and the Italians for three. Differing command structures, national pride and the language barrier all contributed to a lack of cohesion in the application of Allied sea power, producing a situation in which German and Austro-Hungarian U-boat attacks on shipping flourished.