How and where was World War I fought?
As its name implies it was fought throughout the world. The main Battlefield was Belgium and France, mostly in a narrow strip of trench lines running from the coast of France to the Swiss border. In addition there was a huge front running from East Prussia through Austria where Germany and Austria-Hungary fought Russia. In addition secondary fronts in Europe were the Alps between Austrian-Hungary and Italy, Romania which was invaded by the Germans, Salonika in Greece where there was a landing by the allies, and of course Serbia, where the war began. You could also include Ireland where the war began due to the German support for the Irish Republicans.
In the Middle East Britain and France battled the Ottomans on the Egyptian frontier, Palestine, Arabia, and present day Syria and Iraq. It also launched an amphibious landing at Gallipoli in Turkey. Russia and the Ottoman Empire fought in their border areas.
Other campaigns included the British and French war against Germany African Colonies like German East Africa, (today’s Tanzania,) Togo, and Cameroon. Japan and Australia also attacked Germany’s colonies in China, The South Pacific, and New Guinea.
The naval war was truly global with battles off Chile and the Falklands to the Dardanelles. The air war included the first bombardment of cities in Germany and England by Zeppelins and Bomber aircraft. With the exception of the beginning and the end of the war most fronts featured linear trench warfare with little movement and heavy casualties. An exception would be the African campaign and the Middle East which often featured Guerilla warfare
World War One was fought between cousins. Kaiser Wilhelm of Germany was a first cousin to Queen Victoria of England whose surname was Saxe Coburg Gotha until they charmingly changed their name to Windsor. The race to build a German Navy to rival the British Navy coupled with the rapid industrialisation of Germany was sufficient to cause war preparations early 1914. The shooting dead of Austro Hungarian GrandDuke Ferdinand in Sarajevo led to the August 1914 declaration of war with Britain and France facing Germany, Italy and AustroHungary along with Turkey.
The British suffered their firts defeat at the hands of superior German forces at Mons Belgium. Flanders, south Belgium witnessed trench systems stretching until the Swiss border. This was the prime centre of combat with Salonika landings in Serbia an attempt to find a breakthrough against AustroHungarian forces. Italy and the battle of Caporetto where Italian and Austrian troops fought off British and French forces ensured a part of Italy became German speaking. Romania found a young Rommel leading German mountain troops against Romanian forces who were allied with Britain and France.
The largest combat area of World War One was against the Ottoman Empire where Lawrence of Arabia led Arab revolt against poorly led Turkish forces with the eventual capture of Jerusalem and Damascus.
Russia was removed from the war by the shillful tactics of Generalfeldmarshall von Falkenheyn at the battle of the Masurian Lakes in East Prussia. Lenin was allowed to transit Germany to lead the Russian Revolution in 1917.
World War One finished the Ottoman, AustroHungarian, Russian and British Empires.