By mid-September, Germany had been stopped in the west and both sides moved to consolidate their positions with trench warfare. The Germans were more successful in the east, with their much smaller forces pushing back a Russian invasion attempt.
After the German defeat at the Marne, both the Allies and the Germans competed to envelop the northern flank of the opposing army as they fought through Picardy, Artois, and Flanders. The attempts ended when both sides reached the North Sea, ending any possibility of one side outflanking the other.in wikipedia
At the end of the Race to the Sea, the Allied and German armies clashed at Ypres, Belgium. The Germans began by attacking at Langemarck, meeting continued Allied resistance and counterattacks, until heavy losses and the arrival of winter forced the battle to a halt.in wikipedia
In a surprise attack, Ottoman warships bombarded the Russian ports of Odessa and Sevastopol, initiating war with the Russian Empire and bringing the Ottoman Empire into the Great War on the side of the Central Powers.in wikipedia
20 Dec 1914–17 Mar 1915 First Battle of Champagne▲
The French Fourth Army launched a large scale offensive against the Germans in the Champagne Region of France—the first Allied offensive since mobile warfare had been succeeded by trench warfare with the stabilization of the Western Front in October 1914. Although the French General Joffre considered the chances of a breakthrough unlikely due to shortages in materiel, he pursued the attack to pin the Germans down. By the end of the offensive, the French had made minor gains in ground for the cost of over 93,000 casualties—twice as many as the Germans.in wikipedia