From July 23, 1914 it took just fourteen days for all the main powers to become involved in the war.
August 8: French troops crossed the frontier to Mulhouse in Alsace as predicted by the German chief of the general staff.
August 12: 200,000 Austrian troops invaded Serbia, but within a few days they were driven back by the poorly equipped but much larger Serbian army.
August 14: The Battle of Lorraine began south-east of Metz. The French were forced back to Nancy by the German counterattack, but they just managed to stop the German attack.
August 20: French troops clashed with a far larger German force in the Battle of the Ardennes. After four days the French fell back west of the Meuse.
August 21: The British Expeditionary Force (BEF) moved into Belgium to support the French advance.
The French offensive failed completely. Confident that the French armies were on the brink of destruction, two German army corps moved to the eastern front, where the Russians were threatening East Prussia. The already watered-down Schlieffen plan was thus further weakened.
August 23: Japan, which had made an alliance with Great Britain in 1902, declared war on Germany.
August 23: The German First Army struck the BEF near Mons. In the Battle of the Sambre two German armies struck south-west of Namur, on the Sambre River. After the fall of Namur, a general retreat was ordered, British forces were outnumbered and with an unprotected left flank they were forced to withdraw.
August 27: At Le Cateau The French fought off a strong contingent of the German army.
August 29: To relieve German pressure on the British at Le Cateau, the French Fifth Army, itself under pressure from the German Second Army, made a 90-degree shift westward to attack the left flank of the German First Army at Guise. The German advance was blocked, the first French tactical success in the campaign.
The German victories at Mons and Le Cateau convinced their generals that the British forces were no longer a threat. They now marched to the south-east, finally abandoning the remainder of the Schlieffen Plan. Intent on driving the French out of Paris, they continued southward across the Marne, just east of Paris.
September 6-9: First Battle of the Marne, although tactically inconclusive, was an outright strategic victory for the Allies. British and French troops halted German advance just short of Paris. This marked the beginning of trench warfare. The encounter ended the possibility of Germany's winning the war quickly. The Allied nations had far superior resources, and a long war gave them a definite advantage over the Central Powers.
October-November: First Battle of Ypres. Neither side made much progress in any of the battles, despite heavy casualties. At Ypres, the BEF was nearly destroyed while successfully repelling a German drive.
October 10: After taking Antwerp the Germans attempted to break through the British positions in Belgium, but were checked in a series of engagements known collectively as the Battle of Flanders. The Battle of Flanders marked the conclusion of the war of movement or fighting in the open on the western front.
October 29: Turkey declared war against the Allies when Turkish warships co-operated with German warships in a naval bombardment of Russian Black Sea coast.
November 2: Russia formally declared war on Turkey. Battle of the Atlantic. German campaign to prevent merchant shipping from delivering food supplies from the USA to the Allies, chiefly the UK.
November 5: Great Britain responded to the Turkish threat by annexing Turkish Cyprus and with France declared war on Turkey.
December 8: In the South Pacific a squadron of German cruisers was defeated with the loss of four of its five ships in the Battle of Falkland Islands by British naval units.
December 17: Britain declared a protectorate over Egypt (nominally a state subject to Turkey) and began moving troops there to defend the Suez Canal.