The situation looked grim for the Allies early in the year, but a combination of the reinforcements from American troops and general demoralisation of the Germans brought events on the Western Front to a head.
January 8: In an address to Congress, U.S. President Wilson laid down his famous Fourteen Points for peace, calling for open diplomacy, armament reduction, national self-determination, and the formation of a league of nations. These idealistic war aims appeared to give moral weight to the Allied cause.
March 3: Treaty of Brest-Litovsk with Central Powers ended Russian participation in the war, with substantial concessions of territory and reparations. Under the terms of the armistice between Germany and the Allied powers on 11 November, 1918, the Treaty of Brest-Litovsk was annulled since Russia was one of the winning allies.
March 21: Second Battle of the Somme began with German spring offensive. By early 1918, German forces outnumbered the Allies on the Western Front.
March 23: A long-range German cannon began a sporadic bombardment of Paris from a position 65 miles away. This weapon seriously damaged Parisian morale and inflicted 876 casualties, but did not significantly affect the war.
April 9: In the Battle of Lys, the Germans struck the British sector again, this time in Flanders, threatening the important rail junction of Hazebrouck and the Channel ports. German troops quickly broke through unprepared British and one Portuguese division. On 12 April, after announcing, "Our backs are to the wall," Haig forbade further retreat and galvanised British resistance. The German drive was halted on 17 April, after gaining ten miles, that included the recapture of Messines Ridge. There was no breakthrough, and the Channel ports were safe.
May 7: Romania made peace with the Central Powers, signing the Treaty of Bucharest.
July-August:German commanders were still planning a climactic drive against the British in Flanders, and attempted a further offensive in Champagne to lure French troops away from the British front. The Allied forces were forewarned of the blow by deserters, aerial reconnaissance and prisoners. When the Second Battle of the Marne began on 14-15 July, the Allies battered the advancing Germans with artillery. East of Reims the attack was halted within a few hours by the French. West of Reims approximately 14 divisions of the German Seventh Army crossed the Marne, but American forces checked the attack there. Then Allied aircraft and artillery destroyed the German bridges, disrupting supply and forcing the attack to halt on 17 July.
In the space of 5 months the Germans had suffered half a million casualties. Allied losses had been greater, but American troops were now arriving at a rate of 300,000 a month.
The Allied counteroffensive began on 18 July. The French armies, using light tanks and aided by U.S. and British divisions, assaulted the Marne salient from left to right, reaching the Vesle River and recapturing Soissons. The Marne salient no longer existed. Strategically, the Second Battle of the Marne turned the tide; the initiative had been taken from the Germans.
It marked the turning point of World War I. After winning the battle the Allies advanced steadily.
September 27: One day after the beginning of the American offensive, British troops pushed against the Hindenburg line; but this drive soon slowed down in the face of skilful German defence.
Because of American pressure in the Meuse-Argonne, a German retreat all along the line became necessary.
October 6: As the front lines began to crumble, the new German chancellor, Prince Max, of Baden, sent a message to the U.S. President Wilson, requesting an armistice on the basis of Wilson's Fourteen Points.
October 17: In a renewed assault, the British broke through German defences on the Selle River. At the same time the Belgians and British under the Belgian King Albert began to move again in Flanders. The German army began to crack.
October 23: An exchange of messages between the German chancellor and the U.S. President was concluded with Wilson's insistence that the United States and the Allies not negotiate an armistice with the existing military dictatorship of Germany. Immediately before formal dismissal, Ludendorff resigned on 26 October, to permit the desperate German government to comply with Wilson's demand.