Imperial rivalries, the system of alliances and deep-seated animosities helped propel Europe into a general war. However Woodrow Wilson, the US President, ensured America stood apart from Europe's conflict. In August 1914, Germany invaded France and Belgium as part of the Schlieffen Plan. The tiny British Expeditionary Force could only hold up the German army for a few hours at the Battle of Mons, but later joined the French in saving Paris at the Battle of the Marne. The 'Race to the Sea' followed, leading to the First Battle of Ypres, as both sides tried to outflank each other to the north. Their failure led to a stalemate, in which the devastating power of machineguns and artillery forced infantry of both sides to take cover in deep trenches.