After the northern flank of the Western Front had disappeared during the Race to the Sea in late 1914, the Franco-British attacked towards Lille in October, then the BEF, Belgians and the French Eighth Army attacked in Belgium. A German offensive began on 21 October but the 4th Army ( Albrecht, Duke of Württemberg) and 6th Army ( Rupprecht, Crown Prince of Bavaria) were only able to take small amounts of ground, at great cost to both sides, at the Battle of the Yser and further south in the First Battle of Ypres