The Greeks had withdrawn their remaining forces from Anatolia to mainland Greece and Thrace. All indications were that they could no more resist the Turkish army in Thrace than they had been able to do in Anatolia. The Turks swiftly withdrew their army to the border of the Neutral Zone of the Straits. The question was whether the British would attempt to stand in the way of a Turkish attack into Eastern Thrace. They resolved to hold the Straits against the Turks, both to keep their control of the waterway and to retain what they could for the Greeks in Thrace. The French and Italians, on the other hand, realised that standing against the Turks would be folly. They had no desire to do so. The British were to stand alone in defence of the Straits.

There were two potential possibilities for Nationalist attack – the İzmit Peninsula and the South side of the Dardanelles. Both were held only by small British detachments. The danger at the İzmit border was that the Turks could easily defeat a small British force and advance to Istanbul. At the Dardanelles, the Turks could easily take the Southern shore, shell the defences of Gallipoli and likely advance to attack the Greeks in Thrace. Despite Greek protestations that they could defend Thrace, all military assessments were that they would be easily defeated. The Allies had no force capable of assisting the Greeks, and the French and Italians had no desire to do so.

Of the two potential areas for Turkish attack, the assault would probably come at the Dardanelles. The Allied forces in the İzmit Peninsula could be easily defeated and Istanbul taken. The British anticipated that, if Turkish forces moved toward Istanbul, the city would rise in revolt. They doubted if the forces available could put down such a revolt, much less defeat the incoming Turkish army. However, Mustafa Kemal had no desire to attack Istanbul. There would have been little military benefit in taking Istanbul on the way to Thrace, and much of the city might have been destroyed in the attack, with a high civilian death toll. Istanbul would fall readily enough after the Greeks and Allies were defeated.