The Ottoman Empire had not established clear alliances with France or Britain before 1914, so they joined Germany's alliance bloc. Their army provided both Britain and France with a notable front beyond Europe. Turkey provided approximately 600,000 troops (38 divisions) in 1914.
Turkey targeted British and French oil supplies in the Middle East. They were within the proximity of a number of key oil pipelines such as the Anglo-Persian oil pipeline, which was essential to the Royal Navy. The Suez Canal was also a vital supply link for Britain. The early Turkish skirmishes in 1914 and '15 targeted these positions, but their strikes were somewhat ineffective as the British held firm.
In 1915, the British and French expanded their front with the Ottoman Empire. The Gallipoli Campaign was a new plan that outlined how Britain and France could defeat the Ottoman Empire along the Dardanelles Strait. The plan was to seize the Dardanelles with their naval fleets, and from there advance towards, and occupy, the capital of the Turkish Empire. The War Cabinet approved the plan that duly began in early 1915.
However, with heavy naval losses along the Dardanelles the Entente landed troops to occupy the region. Turkey's army established considerable positions along the Dardanelles, which ensured that the Entente troops did not make an effective break out from the shores. During the campaign the Turkish army retook Sulva Bay, and with heavy losses the Entente began to withdraw.
Turkey's army had been more than a match for the British and French at Gallipoli. But their triumphs in the Dardanelles were short-lived as Britain regrouped in 1916 and 1917. Britain dispatched hundreds of thousands of reinforcements to Mesopotamia, and they transformed coastal positions such as Basra into ports where supplies flooded in.
In 1917, the Turkish army had a number of defeats. British troops defeated them in Baghdad, and they made notable advances. But Turkey's soldiers held out at the Battle of Gaza in which the British withdrew. Having held Gaza the Ottoman Empire remained undefeated by 1918, but the British stepped up their advances.
At the Battle of Megiddo Britain won a considerable victory. There Britain and their allies had a notable numerical advantage, which combined with their planes and tanks all but assured victory. Turkey could not match Britain's aircraft and tank support that outflanked their army. From then on the front collapsed as Damascus and Aleppo fell to British forces.
Overall, the Turkish army remained in the war for the duration. But their army was among the smaller in the war, and could not match the British or French forces supported with modern aircraft and tanks. They had won some notable victories such as at Gallipoli, but that was a poorly planned campaign from the outset. Once the British reinforced the front, the Turkish army had relatively little impact in the war and did not occupy any of the notable Entente supply lines and oil fields such as Suez Canal.