Germany entered the First World War in August 1914 with the expectation that the Schlieffen Plan would bring a swift victory. The intention was that the German armies would invade northern France via Belgium and win a rapid victory. This would enable German troops to be transferred to the eastern front to meet the anticipated Russian attack. The plan, however, was unsuccessful.The war on the western front became bogged down as the French held the advance in the Battle of the Marne (September 1914). The pattern of the war in the west changed from one of rapid campaigning to attrition in the trenches. The Battle of Verdun (1916) confirmed the stalemate, with the German forces unable to break through after early victories. A final attempt to end the deadlock was made in the middle of 1918. Again, little ground was won and the German war effort had been exhausted. The Reich suffered increasingly from the blockade of its ports by the Royal Navy, while the entry of the United States into the war in 1917 greatly increased the Allied strength during the course of 1918.