In 1914, the British had few forces in the Persian Gulf, merely a few sloops to represent their interests in the region. The increasing tensions between Britain and the Ottoman Empire led to a decision to reinforce the area. In particular, there was a need to protect the key Anglo-Persian Oil Company refinery at Abadan, which supplied most of the Royal Navy's oil. In October 1914, a brigade of the 6th Indian Infantry Division was sent to establish a forward base at Bahrain. From here, they could easily be moved forwards to Abadan, but were not in a position that was obviously threatening to Ottoman territory. The force arrived in Bahrain on the 23rd of October, but on the 30th, the Ottoman Navy bombarded the Russian Black Sea coast

The Allied force in the Persian Gulf when hostilities began was small: one old battleship, two armed merchants, two sloops and the 16th Infantry Brigade, with preparations underway for a second brigade to arrive. It had two main tasks, protecting the oil facilities at Abadan and denying German cruisers in the Indian Ocean the use of the port of Basra. Both of these required control over the Shatt-al-Arab. This waterway provides sea access to both Abadan and Basra; any reinforcements for Abadan would have to pass through it, as would the German cruisers. The fort at Al-Faw was fairly key to this. It could prevent any Allied merchants or troopships passing it, stopping the British reinforcing Abadan or bringing oil out of it in tankers. As such, it was a vital target. The convoy carrying the 16th Infantry Brigade, escorted by the pre-dreadnought Ocean and the sloop Odin, arrived off Al-Faw on the 3rd November 1914. They spent the next day preparing, before landing on the 5th with 600 men of the 16th Brigade, a party of Royal Marines and a section of artillery guns. The fort fell quickly, with little resistance. On the 7th-8th, the brigade moved forward to take up positions north of Abadan, blocking any Ottoman advance on the refinery.

On the 14th November, the remainder of the 6th Indian Division arrived. This allowed the Allied force to push towards Basra. A brief, but hard-fought action took place on the 17th at Sahil, south of the city. The Ottoman defenders were defeated, but the Allied force was successfully delayed. The Ottomans attempted to dig in along a new defensive line, but this was outflanked by Allied troops moved along the river by ship. Basra fell on the 20th November. This success allowed the British to put more pressure on the Sheikh of Kuwait. A new treaty was signed, which fully established Kuwait as a British protectorate, rather than as a strange superposition of British protectorate and autonomous Ottoman region.

Further advances into Iraq continued along the Tigris and Euphrates rivers from Basra, rather than overland from Kuwait. This was because moving along the river greatly simplified the logistics of the campaign. With the resources of the Royal Navy, large amounts of supplies could easily be moved along the river. There was less of a need for fresh water, with the river nearby and easily accessible. An overland campaign through the desert would have more of a need for fresh water, and would need many more trucks or horses to replace the mobility advantage that the waterways offered.