Key Battles of World War One

The war drew in all of the European powers after Germany enacted the Schlieffen Plan. Germany invaded France through the flat and accessible terrain of Belgium on the 1st August 1914. The British, keen to ensure that Germany did not get hold of French and Belgian ports and wishing to protect Belgian neutrality, declared war on Germany.

Phases:

Phase one - the race for the sea (1914):

After the British and French halted the German advance through Belgium and northern France in autumn 1914, both sides raced to control the nearby North Sea coastline.

Phase two - static trench warfare (1915 - 1917):

A Front line was established running through Belgium and northern France. The two sides established trench system. The war was primarily in a situation of stalemate.

Phase three - a war of movement again (1918):

The German high command decided to launch one final push against the Allies on the Western Front in the spring of 1918. Initial successes were short-lived however and by November, the allies had defeated the German army on the Western Front.  

Battles:

• Battle of the Falkland Islands - December 8th 1914, the British decimated the German East Asia Squadron during an attack on the Falkland Islands in the South Atlantic.
• Battle of the Marne - September 5th 1914 - September 9th, the Allied forces, following their retreat from Mons, stopped the German forces on the banks of the Marne River and forced them back forty five miles to the river Aisne.
• Battle of Mons - August 23rd 1914, one of the earliest battles on the Western Front. The German advance in Belgium overwhelmed British and French forces who began a fourteen day retreat to the outskirts of Paris.
• Battle of Passchendaele - September 20th 1917 - October 12th, the British forces in Belgium continued to push the Germans back. The fighting was especially miserable because it was carried out during periods of heavy rain.
• Battle of the Somme - July 1st 1916 - November 18th, one of the biggest battles of the war fought in northern France. The battle of the Somme was the result of an allied offensive along a twenty five mile front. Although it ended up as a small victory for the allied powers, it cost them 146000 lives in order to advance less than six miles.    

http://www.home.zonnet.nl/rene.brouwer/majorbattles.htm
http://yesterday.uktv.co.uk/warzone/world-war-one/article/western-front-key-wwi-battles/