The 'Battle of Madagascar' was fought between British-led and Vichy French forces for control of the island of Madagascar in the Indian coast off the eastern coast of Africa (5 May/6 November 1942).

The seizure of the island by the British was planned to deny the use of Madagascar’s ports by the Imperial Japanese navy and to prevent the loss or impairment of the Allied shipping routes to India, Australia and South-East Asia. The campaign began with the 'Ironclad' seizure of the port of Diego Suárez (now Antsiranana) near the northern tip of the island on 5 May 1942. A subsequent campaign to secure the entire island, 'Stream Line Jane', was opened on 10 September, and in this the British-led forces made a number of other landings and then broke into the interior, linking with other forces to secure the island by the end of October. Fighting ceased and an armistice agreed on 6 November.

This was the first large-scale Allied operation combining sea, land and air forces, and following the end of the campaign the island was placed under Free French control.

Diego Suárez is a large bay, with a good harbour, near the northern tip of Madagascar. It has an opening to the east through the Oronjia Pass, a narrow channel. The naval base of Diego Suárez lies on a peninsula between two of the four small bays enclosed within Diego Suárez Bay, which cuts deeply into the northern tip of Madagascar’s Cape Amber, almost severing it from the rest of the island. In the 1880s the bay was coveted by France, which claimed it as a coaling station for steamships making passage to and from French possessions farther to the east. The colonisation was formalized after the first Franco-Hova War when Queen Ranavalona III signed a treaty on 17 December 1885 giving France a protectorate over the bay and surrounding territory; as well as the islands of Nossi-bé and Ste Marie de Madagascar. The colony’s administration was subsumed into that of French Madagascar in 1897.

By 1941, Diego Suárez town, the bay and the channel were all well protected by naval shore batteries.

Following the Japanese conquest of South-East Asia to the east of Burma in the period up to the end of February 1942, Japanese submarines moved freely throughout the north and eastern expanses of the Indian Ocean. In March, Japanese aircraft carriers raided merchant ships in the Bay of Bengal, and attacked bases in Colombo and Trincomalee in Ceylon (now Sri Lanka). This raid drove the British Eastern Fleet out of the area in a relocation to a new base at Kilindini Harbour neat Mombasa in Kenya. The move made the British fleet more vulnerable to attack, and the possibility of Japanese naval forces using forward bases in Madagascar was a problem which had to be addressed. The possible use of these facilities particularly threatened Allied merchant shipping, and especially the supply routes to the British 8^th Army in North Africa and also the Eastern Fleet.

Japanese 'Kaidai' class large fleet submarines had the longest range of any Axis submarines at the time, extending to more than 10,000 miles (16095 km) in some cases, but being challenged by the US Navy’s then-relatively new 'Gato' class fleet submarines' 12,665-mile (20385-km) maximum range. If the Imperial Japanese navy’s submarines could use bases on Madagascar, Allied lines of communication would be affected across a region stretching from the Pacific and Australia, to the Middle East and indeed as far as the South Atlantic.

On 17 December 1941, Vizeadmiral Kurt Fricke, the chief-of-staff of Germany’s Seekriegsleitung (maritime warfare command) met Vice Admiral Naokuni Nomura, the Japanese naval attaché, in Berlin to discuss the delimitation of respective operational areas between the German and Japanese naval forces. At another meeting, on 27 March 1942, Fricke stressed the importance of the Indian Ocean to the Axis powers and expressed the desire that the Japanese begin operations against the northern Indian Ocean sea routes. Fricke further emphasised he fact that Ceylon, the Seychelles islands group, and Madagascar should have a higher priority for the Axis navies than operations against Australia. By 8 April, the Japanese had told Fricke that they intended to commit four or five submarines and two auxiliary cruisers for operations in the western part of the Indian Ocean between Aden and the Cape of Good Hope, but refused to disclose their plans for operations against Madagascar and Ceylon, reiterating merely their commitment to operations in the area.

The Allies had heard the rumours of Japanese plans for the Indian Ocean, and on 27 November 1941 the British Chiefs-of-Staff discussed the possibility that the Vichy French government might cede the whole of Madagascar to Japan, or alternatively permit the Japanese navy to establish bases on the island. British naval advisors therefore urged the occupation of the island as a precautionary measure.  On 16 December, Général de Brigade Charles de Gaulle, leader of the Free French movement in London, sent a letter to the British prime minister, Winston Churchill, uriging a Free French operation against Madagascar. Churchill recognised the risk of a Japanese-controlled Madagascar to Indian Ocean shipping, particularly to the important sea route to India and Ceylon, and considered the port of Diego Suárez as the strategic key to Japanese influence in the Indian Ocean. However, he also made it clear to planners that he felt the UK currently lacked the resources to mount such an operation and, following experience in the 'Battle of Dakar' in September 1940 as 'Menace', did not wish a joint operation launched by British and Free French forces to secure the island.

By 12 March 1942, Churchill had been convinced of the importance of such an operation, however, and the decision was reached that the planning of the invasion of Madagascar would begin in earnest. It was agreed, though, that the Free French would be explicitly excluded from the operation. As a preliminary battle outline, Churchill gave the following guidelines to the planners of what was at the time schemed as 'Bonus: Vice Admiral E. N. Syfret’s Force 'H', the ships guarding the Straits of Gibraltar and the western basin of the Mediterranean Sea, should move south from Gibraltar and be replaced by a US task force; the 4,000 men and ships proposed by Vice Admiral the Lord Mountbatten for the operation, should be retained as the nucleus around which the plan should be built; the operation should be launched on about 30 April 1942; and in the event of success, the commandos recommended by Mountbatten should be replaced by garrison troops at the earliest possible moment.

On 14 March, Force 121 was constituted under the command of Major General R. G. Sturges of the Royal Marines with Syfret in command of the naval Force 'H' and the other elements of the supporting sea forces. Force 121 departed the Clyde river in Scotland on 23 March and joined Syfret’s ships at Freetown in Sierra Leone, proceeding thence in two convoys to their assembly point at Durban on the South African east coast. Here they were joined by Brigadier D. N. Wimberley’s 13^th Brigade Group of Major General H. P. M. Berney-Ficklin’s British 5^th Division. Sturges’s force now comprised three infantry brigades, while Syfret’s squadron consisted of the the battleship Ramillies (flag), aircraft carriers Illustrious and Indomitable, heavy cruiser Devonshire, light cruiser Hermione, 11 destroyers, six corvettes, six minesweepers and a number of auxiliary units. It was a formidable force to bring against the 8,000 Vichy French troops, most of them conscripted Malagasies, at Diego Suárez, but the chiefs of staff were adamant that the operation was to succeed, preferably without any fighting.

This was to be the first British amphibious assault since the landings at the start of the disastrous Dardanelles campaign in 1915.

During the assembly in Durban, Field Marshal Sir Jan Smuts, the prime minister of South Africa, pointed out that the mere seizure of Diego Suárez would be no guarantee against continuing Japanese aggression and urged that the ports of Majunga and Tamatave, on Madagascar’s north-western and north-eastern coasts, also be occupied. This suggestion was evaluated by the Chiefs-of-Staff, but it was decided, on the basis of lack of manpower, to retain Diego Suárez as the only objective. Churchill remarked that the only way to effect the permanent security of Madagascar was by means of a strong fleet and adequate air support operating from Ceylon, and sent General Sir Archibald Wavell, the commander-in-chief in India, a note stating that as soon as the initial objectives had been met, all responsibility for safeguarding Madagascar would be passed to Wavell. Churchill added that when the commandos were withdrawn, garrison duties would be performed by two African brigades and one brigade from the Belgian Congo or the west coast of Africa.

In March and April, aircraft of the South African Air Force had undertaken reconnaissance flights over Diego Suárez and Nos 32, 36 and 37 Coastal Flights were withdrawn from maritime patrol operations and sent to Lindi on the Indian Ocean coast of Tanganyika, with an additional 11 Bristol Beaufort twin-engined torpedo bombers and six Martin Maryland twin-engined light bombers to provide close air support during the planned operation.

The Allied commanders had decided to launch an amphibious assault on Madagascar as 'Ironclad' executed by Force 121. It included Allied naval, land and air forces, and was commanded by Sturges. The British army landing force included Brigadier F. W. Festing’s 29^th Independent Brigade Group, No. 5 (Army) Commando, and two brigades of the 5^th Division, the latter en route to India with the remainder of their division. The Allied naval contingent comprised more than 50 vessels drawn from Force 'H', the British Home Fleet and the British Eastern Fleet, commanded by Syfret.

Following many reconnaissance sorties by South African aircraft, the first wave of the 29^th Independent Brigade Group and No. 5 Commando landed in assault craft on 5 May, two brigades of the 5^th Division and Royal Marines following in several waves. All were carried ashore by landing craft to Courrier Bay and Ambararata Bay, just to the west of the major port of Diego Suárez at the northern tip of Madagascar. A diversionary attack was staged to the east. Air cover was provided mainly by Fairey Albacore and Fairey Swordfish singler-engined torpedo bombers which attacked Vichy French shipping and the airfield at Arrachart. The torpedo bombers were supported by Grumman Martlet single-engined fighters of the Fleet Air Arm, and a small number of SAAF aircraft assisted. The Swordfish torpedo bombers sank the armed merchant cruiser Bougainville and then the submarine Bévéziers, although one Swordfish was shot down by anti-aircraft fire and its crew was taken prisoner: this aeroplane had been dropping French-language leaflets encouraging the Vichy French troops to surrender.

The defending Vichy French forces, led by the governor general, Armand Léon Annet, included about 8,000 troops, of whom some 6,000 were Malagasy tirailleur colonial infantry. A large proportion of the rest were Senegalese. Between 1,500 and 3,000 Vichy French troops were concentrated in the Diego Suárez area, but their supporting naval and air defences were relatively light and/or obsolete: eight coastal batteries, two armed merchant cruisers, two sloops, five submarines, 17 Morane-Saulnier MS.406 single-engined fighters fighters and 10 Potez 63 twin-engined light bombers.

The landings met almost no resistance and the landed troops seized Vichy French coastal batteries and barracks. The Courier Bay force, Brigadier G. W. B. Tarleton’s 17^th Brigade forced its way with difficulty through mangrove swamp and thick bush before taking the town of Diego Suárez and 100 men prisoner. The Ambararata Bay force, the 29^th Independent Brigade, headed towards the French naval base of Antisarane. With assistance of six Valentine infantry tanks of 'B' Special Service Squadron and six Tetrarch light tanks of 'C' Special Service Squadron, the 29^th Independent Brigade advanced 21 miles (34 km), overcoming light resistance with bayonet charges. Antisarane itself was heavily defended with trenches, two redoubts, pillboxes, and on both flanks essentially impenetrable swamps. Arrachart airfield was attacked, five of the Morane-Saiulnier fighters being destroyed and another two damaged, while two Potez-63 aircraft were also damaged. This attack effectively reduced by one-quarter the Vichy French air strength on the island. Two MS.406 fighters made a brief appearance and strafed beaches in Courier Bay, but two more Vichy French aircraft were lost on this first day.

During the morning of 6 May a frontal assault on the defences failed with the loss of three Valentine and two Tetrarch tanks. Three Potez 63 warplanes attempted to attack the beach landing points but were intercepted by Martlet fighters, which shot down two of the Vichy French aircraft. Albacore aircraft were used to bomb French defences, while one Swordfish managed to sink the submarine Le Héros. By the end of the day, fierce resistance had resulted in the destruction of 10 of the 12 tanks the British had brought to Madagascar. The British had been unaware of the strength of the French defences known as the 'Ligne Joffre', and were greatly surprised at the level of resistance they had met. Another assault by the 2/South Lancashire Regiment worked its way around the Vichy French defences, but the swamps and bad terrain meant the British attackers were broken into groups but nevertheless swung behind the Vichy French line and caused chaos. Fire was poured on the Vichy French defences from behind, and the radio station and a barracks were captured. In all, 200 prisoners were taken, but the South Lancashires had to withdraw as communication with the main force was nonexistent after a radio failure. At this time, the Vichy French government in France began to learn of the landings, and Amiral de la Flotte François Darlan sent a message to Annet telling him to 'firmly defend the honour of our flag, and to 'fight to the limit of your possibilities… and make the British pay dearly'. The Vichy French forces then asked for assistance from the Japanese, who were in no position to provide substantial support.

With the Vichy French defence highly effective, the deadlock was broken when the old destroyer Anthony dashed straight past the harbour defences of Antisarane and landed 50 Royal Marines from Ramillies in the Vichy French rear area. The marines created a 'disturbance in the town out of all proportion to their numbers', taking the French artillery command post along with its barracks and the naval depot. At the same time the troops of the 17^th Brigade had broken through the defences and were soon marching into the town. The Vichy French defence was broken and Antisarane surrendered during that evening, although substantial Vichy French forces withdrew to the south. On 7 May British Martlet fighters encountered three MS.406 fighters, one Martlet being shot down. All three of the French fighters were then shot down, meaning that by the third day of the attack on Madagascar, 12 Morane-Saulnier MS.406 and five Potez 63 aircraft had been destroyed out of a total of 35 Vichy French aircraft on the entire island. Another three Potez bombers were destroyed on the ground during a raid on Majunga on 15 May. Fighting continued into 7 May, but by the end of this day 'Ironclad' had effectively concluded. In just three days of fighting the British had seen 109 men killed and 283 wounded, with the French suffering 700 casualties.

The Japanese submarines I-10, I-16 and I-20 arrived three weeks later on 29 May. I-10's reconnaissance floatplane spotted Ramillies at anchor in Diego Suárez harbour, but the floatplane was spotted and Ramillies changed her berth. I-20 and I-16 launched two midget submarines, one of which managed to enter the harbour and fire two torpedoes while under depth charge attack from two corvettes. One torpedo seriously damaged Ramillies, while the second sank the 6,993-ton tanker British Loyalty, which was later refloated. Ramillies was later repaired in Durban and Plymouth.

The crew of one of the midget submarines, Lieutenant Saburo Akieda and Petty Officer Masami Takemoto, beached their M-20b at Nosy Antalikely and moved inland towards their pick-up point near Cape Amber. They were betrayed when they bought food at the village of Anijabe and both were killed in a firefight with Royal Marines three days later. One marine was also killed in the action. The second midget submarine was lost at sea and the body of a crewman was found washed ashore a day later.

Hostilities continued at a low level for several more months. After 19 May two brigades of the 5^th Division were transferred to India. On 8 June, Brigadier W. A. Dimoline’s 22^nd (East Africa) Brigade Group arrived on Madagascar, and Brigadier G. T. Seneschal’s South African 7^th Motorised Brigade arrived on 24 June. On 2 July, an invasion force was sent in 'Throat' to the Vichy French-held island of Mayotte in order to take control of its valuable radio station and to make use of it as a base for British operations in the area. The island’s defenders were caught by surprise and the key radio station and most of the sleeping defenders were taken prisoner. The police chief and a few others attempted to escape by car but were stopped at a roadblock. The island’s capture was carried out with no loss of life or major damage.

Brigadier R. E. Hobday’s 27^th (North Rhodesia) Brigade, which included East African elements, landed on Madagascar during 8 August. Annet, the Vichy French governor of Madagascar, attempted to obtain reinforcements, especially of aircraft, from the Vichy government in France, but was unable to do so. By August, the Vichy French air strength on the island comprised primarily only four Morane-Saulnier fighters and three Potez 63 multi-role warplanes.

An operation codenamed 'Stream Line Jane' (sometimes given as 'Streamline Jane') consisted of three separate sub-operations codenamed 'Stream', 'Line' and 'Jane'. 'Stream' and 'Jane' were, respectively, the amphibious landings at Majunga on 10 September and Tamatave on 18 September, while 'Line' was the advance from Majunga to the Vichy French capital, Tananarive, which fell on 23 September.

On 10 September the 29^th Brigade and 22^nd Brigade Group made an amphibious landing at Majunga, a port on the island’s north-western coast. No. 5 Commando spearheaded the landing and faced machine gun fire but nonetheless stormed the quayside, took control of the local post office, seized the governor’s residence and raised the Union flag. Having cut communications with Tananarive, the Allies intended to relaunch the offensive ahead of the rainy season, but progress was slow. In addition to occasional small clashes with Vichy French forces, the British also encountered scores of obstacles erected on the main roads by Vichy French soldiers, who also attempted to destroy the second bridge on the road linking Majunga and Tananarive but succeeded only in causing the bridge’s central span to sag some 3 ft (1 m) into the river below but not preventing Allied vehicles from crossing. Once the Vichy French forces had realised their mistake, a Potez 63 was sent to bomb the bridge, but the attack failed. The Allies eventually captured the capital, Tananarive, on 23 September and without much opposition, and then the town of Ambalavao, but Annet escaped.

Eight days later a British force set out to capture Tamatave, where the presence of heavy surf interfered with the operation. As the launch of the cruiser Birmingham was heading toward the shore, it was engaged by French shore batteries and promptly turned back. Birmingham then opened fire on the shores batteries and within three minutes the Vicht French raised a white flag and surrendered. From there the 2/South Lancashire and 2/Royal Welch Fusiliers set out to the south to link with forces there. After reaching Tananarive, the two battalions pressed on toward Moramanga and on 25 September linked with the King’s African Rifles having secured the British lines of communication around the island. At the same time the East African infantry and South African armoured cars set out to find the elusive Annet. On the same day, a raid was launched by South African Maryland bombers on a Vichy French fort in Fianarantsoa, the only major centre of population still in opposition hands and where the remainder of the Vichy French aircraft were now based. Tetrarch and Valentine tanks of 'B' and 'C' Special Service Squadrons had been embarked for use in these operations, but were not used as they could not ford the Ivondro river and the railway bridges were unsuitable.

On 29 September, two companies of the South African Pretoria Highlanders performed the only amphibious landing by South African forces of the entire war at the west-coast harbour town of Tuléar some 900 miles (1450 km) to the south of the island’s northern tip. Birmingham, two destroyers and 200 Royal Marines supported the unopposed landing.

On 6 October, a Morane-Saulnier fighter strafed British positions near Antinchi, and on 8 October a British bombing raid on Ihosy airfield destroyed four Vichy French aircraft.

The last major action took place on 18 October, at Andramanalina, a U-shaped valley carrying the meandering Mangarahara river, where the Vichy French planned an ambush for British forces. The King’s African Rifles split into two columns and marched around the 'U' of the valley and met Vichy French troops in the rear and then ambushed them. The Vichy French troops suffered heavy losses, and 800 of them surrendered. A single Morane-Saulnier fighter was operational until 21 October, and even strafed South African troops, but by 21 October the only serviceable aeroplane still left to the Vichy French was a Salmson Phrygane single-engined light transport. On 25 October the King’s African Rifles entered Fianarantsoa but found Annet gone, this time to a position near Ihosy, 100 miles (160 km) to the south. The East Africans swiftly moved after him, but received an envoy from Annet asking for terms of surrender. An armistice was signed in Ambalavao on 6 November, and Annet surrendered two days later.

The Allies had suffered about 500 casualties in the landing at Diego Suárez, and 30 more killed and 90 wounded in the operations which followed on 10 September 1942.

With Madagascar in their hands, the British established military and naval installations across the island, which remained of importance for the rest of the war. Its deep-water ports were vital for control of the passages to India and the Persian corridor, and were now beyond the grasp of the Axis. A Free French officer, Général de Division Paul Legentilhomme, was appointed high commissioner for Madagascar in December 1942 in succession to a British administration.