At the end of the war with Turkey the British Cabinet (Lord Curzon in particular) wanted to ensure that Turkey could never threaten British interests again. Initially it was suggested that the Ottoman Empire be completely broken up and the Turks expelled from European Turkey (including Constantinople) to safeguard the Dardanelles. The Empire was also to be stripped of possessions in Armenia and the Arab lands. As the treaty negotiations began in January 1920, the Cabinet modified this programme and made the demilitarisation and internationalisation of the straits a central element of the peace terms.
By the mid 1920s, however, the Ottoman administration based in Constantinople was being rapidly replaced by Mustafa Kemal's nationalist movement based in Ankara. In June 1920 before the Treaty of Sevres could be signed, Turkish resistance to its terms had increased Kemal's supporters (including those in Constantinople), and his forces advanced on the practically undefended straits.
The Cabinet was determined to defend the straits, despite the lack of British forces to send. Instead, the Greeks were co-opted, with the understanding that the Greek enclave of Smyrna would be enlarged if they helped to destroy Turkish nationalism. In 1921 the unpredictable nature of the Greek-Turkish war and the view that the Greeks were often close to victory helped Lloyd George and Curzon defend the government's policy from within the Cabinet.
By late 1921 the French and Italians were showing impatience with British policy in the region. In March 1922 Britain, France and Italy agreed on revised terms to be provisionally offered to the Ottoman authorities, and to Kemal. Yet again, the British insisted that the Turkish military must be kept away from the straits, although by smaller demilitarised zones than had been previously suggested.
Matters were brought to a head with the defeat of Greek forces in Asia Minor and the capture of Smyrna by Kemalist forces in August and September 1922. On the 7 September the Cabinet decided to defend the straits and Constantinople. By 15 September both the Admiralty and the War Office had raised concerns about the practicalities of the policy, but the Cabinet remained adamant that the straits must not fall under Turkish military control. As Kemal's forces continued marching towards the straits, Cabinet consensus on defending Constantinople started to collapse, and resulted in the decision not to hold the city.
Attention now centred on Chanak. The British believed that Chanak controlled the Dardanelles (through which all reinforcements and supplies for the defence of Constantinople passed) and that it would serve as an outpost for the defence of the Gallipoli Peninsula - the key to the whole straits. Chanak therefore was given the highest priority for resources.
On 29 September the Cabinet received a telegram from the Commander of the British garrison in Chanak, General Harrison. It read that the Kemalist forces had advanced right up to the defences. The Cabinet sent Harrison an ultimatum to be passed on to Kemal: withdraw or be fired upon. Harrison ignored the Cabinet's instructions and instead embarked on negotiation with Kemal; however, the negotiations broke down on 5 October.
After intense Cabinet discussion, it was decided that without the support of France or Italy, strict neutrality was the only course of action remaining. This neutrality involved withdrawal to Chanak and Gallipoli, leaving the French and Italians without support in Constantinople. The French pledged their support for an allied policy of refusing to admit the Turkish into the Eastern Thrace until a treaty had been signed. Four days later the Turks agreed to allied terms, and a stop to all military operations in the neutral straits zone.
Events at Chanak and the threat of war over the Dardanelles greatly damaged Lloyd George's ability to control his coalition government and the end of the month Lloyd George's government had collapsed, paving the way for the Conservatives to take power.