アングロ＝イラク戦争
Further exchanges of messages took place between the British and Iraqi forces but none were able to defuse the situation. Air Vice-Marshal Smart again requested reinforcements and this time Air Officer Commanding Sir Arthur Longmore ordered 18 Vickers Wellington bombers to RAF Shaibah. The British Ambassador signalled the Foreign Office that he regarded the Iraqi actions as an act of war, which required an immediate air response. He also informed them that he intended to demand the withdrawal of the Iraqi forces and permission to launch air strikes to restore control, even if the Iraqi troops overlooking Habbaniya did withdraw it would only postpone aerial attacks.
On the morning of 15 April, Convoy BP7 was met at sea by HMS Seabelle from Basra. Later in the day the escort was reinforced by HMS Falmouth. On 17 April, the convoy was joined by HMIS Lawrence and then proceeded towards the entrance of the Shatt al-Arab. On 18 April, the convoy moved up the Shatt al-Arab and arrived at Basra at 0930 hrs. HMS Emerald was already in Basra. On the same day, HMNZS Leander was released from support duties in the Persian Gulf. On 16 April, the Iraqi Government was informed that the British were going to invoke the Anglo-Iraq treaty to move troops through the country to Palestine. Rashid Ali raised no objection.
The 20th Indian Infantry Brigade included the 2nd battalion 8th Gurkha Rifles, 2nd battalion 7th Gurkha Rifles, and the 3rd battalion 11th Sikh Regiment. The landing of the force transported by Convoy BP7 was covered by infantry of the 1st KORR which had arrived the previous day by air. The landing was unopposed.
By 19 April, the disembarkation of the force transported by Convoy BP7 at Basra was completed. On the same day, seven aircraft were flown into RAF Habbaniya to bolster the air force there. Following the landing of the 20th Indian Infantry Brigade, Rashid Ali requested that the brigade be moved quickly through the country and that no more troops should arrive until the previous force had left.
On the night of 27 May, the British advance on Baghdad began. The advance made slow progress and was hindered by extensive inundations and by the many destroyed bridges over the irrigation waterways which had to be crossed. Faced with Clark's advance, the government of Rashid Ali collapsed. On 29 May, Rashid Ali, the Grand Mufti, and many members of the "National Defence Government" fled to Persia. After Persia, they went on to Germany. On the morning of 31 May, the Mayor of Baghdad and a delegation approached British forces at the Washash Bridge.
By the end of the month, Colonel Roberts and 300 of the 1st KORR had been flown from RAF Shaibah to RAF Habbaniya to reinforce the latter base. Other than the 1st KORR, there were no trained British troops at Habbaniya bar the Number 1 Armoured Car Company RAF.
The principal difficulty was that there were insufficient troops to take over Maqil, Ashar, and Basra City concurrently. While the Iraqi troops in Basra agreed to withdraw on 2 May, they failed to do so. On 6 May, the 21st Indian Infantry Brigade under the command of Brigadier Charles Joseph Weld arrived and disembarked at Basra. This was the 10th Indian Infantry Division's second brigade to arrive in Iraq. The 21st Indian Infantry Brigade included 4th battalion 13th Frontier Force Rifles, 2nd battalion 4th Gurkha Rifles, and 2nd battalion 10th Gurkha Rifles.
On 22 May, the Iraqi 6th Infantry Brigade, of the Iraqi 3rd Infantry Division, conducted a counter-attack against the British forces within Fallujah. The Iraqi attack started at 02:30 hours supported by a number of Italian-built L3/35 light tanks. By 03:00 the Iraqis reached the north-eastern outskirts of the town. Two light tanks, which had penetrated into the town, were quickly destroyed. By dawn British counter-attacks had pushed the Iraqis out of north-eastern Fallujah. The Iraqis now switched their attack to the south-eastern edge of the town. But this attack met stiff resistance from the start and made no progress.
British forces were to remain in Iraq until 26 October 1947 and the country remained effectively under British control. The British considered the occupation of Iraq necessary to ensure that access to its strategic oil resources be maintained. On 18 August 1942, General Maitland Wilson was appointed Commander-in-Chief of the Persia and Iraq Command. By 15 September, he was headquartered in Baghdad.
3月31日、イラクの摂政であるアブドゥル・イラー王子は自分を逮捕する計画の存在を知り、バグダードからハバニヤ基地へ、ハバニヤからバスラに逃亡し、砲艦HMSコックチェーファーに避難した。その翌日、ラシッド・アリと、「ゴールデンスクエア」と呼ばれる4人の軍司令官がクーデターで権力を掌握し、ラシッド・アリは自らを「国防政府の首長」と宣言した。ゴールデンスクエアはタハ・アル・ハシミ首相に関する証言を集め、ラシッド・アリは再びイラクの首相になった。アリは君主制には反対せず、シャラフ・ビン・ラジェをファイサル2世の摂政としたが、ファイサル2世本人と王族はムラ・エフェンディの家に避難していた。ゴールデンスクエアも親英市民と政治家を逮捕したが、多くは英領トランスヨルダンへ逃亡した。
ゴールデンスクエアは、英国への譲歩の拒否、イタリアとの外交関係の維持、親英国の政治家を追放することを目的としていて、イギリスが弱いという前提での交渉を行った。クーデターから二週間が経った4月17日、アリはイギリスとの戦争が起きた際の軍事援助をドイツに求め、また、イラクに到着したイギリス軍が英領パレスチナへ移動すると主張し、1930年の条約の第5条に基づいてイギリスの権利を制限しようとした。