sentences:  German naval forces in the Baltic were reinforced by elements of the High Seas Fleet during the Battle of the Gulf of Riga in early August 1915.The Germans sought to drive out the Russians in the Gulf of Riga and to lay defensive minefields that would prevent a Russian counterattack.The battleships of the I Battle Squadron were the primary force, though "Prinz Heinrich" and the rest of the older vessels assigned to the Baltic fleet participated.