United Kingdom Vichy France The Battle of Deir ez-Zor was part of the Allied invasion of Syria during the Syria-Lebanon campaign in World War II.

On 8 June 1941, the Allies had launched attacks from the British mandate of Palestine and Trans-Jordan in the south into Lebanon and south-west Syria.

By 20 June, Damascus had been captured, and the Allied campaign commander Henry Maitland Wilson ordered two further attacks from western Iraq toward Palmyra and Aleppo.

The advance units of 10th Indian Division left Haditha on 27 June and captured Abu Kamal without opposition.

Progress on the poor road was slow and made more difficult by air attacks from Vichy aircraft but by early afternoon there were units within 9 miles of Deir ez-Zor.

Slim decided that the risk was justified by the opportunity it afforded of taking the Vichy defenders by complete surprise.