The 'Battle of Gabon' was the Free French campaign to take control of Gabon from the Vichy France and also to rally French Equatorial Africa to Free France (27 October/12 November 1940).

In June 1940 Germany completed its defeat of France, and subsequently occupied the major part of that country. Maréchal de France Philippe Pétain established a collaborationist government in Vichy to administer unoccupied French territory. On 18 June Général de Brigade Charles de Gaulle, now based in the UK, broadcast a radio appeal to his compatriots abroad, calling on them to reject the Vichy French régime and join the UK in its war against Germany and Italy. The broadcast provoked division in France’s African territories, where colonists were forced to choose sides.

On 26 August, the governor and military commanders in the colony of French Chad announced that they were rallying to de Gaulle’s Free French Forces. A small group of Gaullists seized control of French Cameroon during the morning of the following day, and on 28 August a Free French official ousted the pro-Vichy governor of French Congo. The next day the governor of Ubangi-Shari declared that his territory would support de Gaulle, though his declaration prompted a brief struggle for power with a pro-Vichy French army officer, but by the end of the day all but one of the colonies that constituted French Equatorial Africa had rallied to Free France: the exception was French Gabon. On the evening of 28/29 August 1940, the colony’s governor, Georges Masson, had pledged Gabon’s allegiance to Free France, but then faced immediate opposition from much of Libreville’s French population and from Gabon’s influential Catholic bishop, Louis Tardy, a conservative who favoured Vichy France’s anti-Freemason policies. In the face of this pressure, Masson was forced to rescind his pledge, and Free French sympathisers were subsequently arrested and either imprisoned on board the auxiliary cruiser Cap des Palmes or deported to Dakar in the pro-Vichy West African colony of Senegal. Perturbed by Gabon’s refusal to join his cause, de Gaulle later described his dilemma as that of 'a hostile enclave, which was hard to reduce because it gave on to the ocean, [had been] created in the heart of our equatorial holdings'. Edgar de Larminat, then a colonel and the governor general of French equatorial Africa, stated that the failure to secure the territory would threaten 'the very principle of our presence in Africa'.

After Cameroon had rallied to the Free French cause on 27 August, the Gabonese authorities decided to reinforce their frontier with that province along with the Ntem river. On 3 September, one Roger Gardet entered Bitam by a ruse: on the pretext of medical necessity, he received permission from Capitaine Gourvès at Bitam to cross the frontier. Gourvès agreed to rally his troops to Free France only if his superior, one Besson, who was the chief administrator of Woleu-Ntem based at Oyem also did so. Besson initially refused, but on 5 September Gardet told him that he was relieving him of his command. Besson left for Cameroon and the next day, 6 September, Free French forces arrived in Bitam and Oyem with Pierre Roger Martocq as the new administrator of Woleu-Ntem.

On 11 September, Masson held a meeting with his army and navy commanders, and it was decided to reinforce Mayumba. On 9 and 15 September, Colonel André Parant brought a dozen Free French irregulars into Mayumba in a Potez 540 twin-engined multi-role aeroplane. On 15 September, Vichy French reinforcements arrived on the Cap des Palmes, escorted by the submarine Poncelet: these were a troop of marines from the aviso (colonial sloop) Bougainville to defend Port Gentil, Gabon’s second-largest city. While the submarine’s commander, Capitaine Bertrand de Saussine du Pont de Gault, was taking breakfast with the district administrator, the Free French entered the administrator’s residence. After several hours of discussions, and with Parant’s men occupying the city, Saussine was allowed to leave, taking with him any who did not wish to join the Free French. Most of the marines opted to stay in Mayumba.

On 8 October, de Gaulle arrived in Douala, the capital of Cameroon, and four days later authorised plans for the invasion of French Equatorial Africa, which he planned to use as the base from which to launch attacks into Axis-controlled Libya. For this reason, he personally headed to the north in order to survey the situation in Chad on the southern border of Libya.

On 27 October, Free French forces crossed into French Equatorial Africa and took the town of Mitzic. On 5 November, the Vichy garrison at Lambaréné capitulated. Meanwhile, the main Free French forces under Colonel Philippe Leclerc de Hauteclocque and Commandant Marie Pierre Koenig left Douala in Cameroon to take Libreville in French Equatorial Africa. The British were doubtful of de Gaulle’s ability to establish control over the Vichy territory, but agreed to lend a measure of naval support to the Free French. John Hasey, an officer of the Foreign Legion, reported that after the first few days of fighting, 150 prisoners had been taken and joined the Free French a few weeks later: 'curiously enough, no one tried to convince them. They argued it out among themselves and joined up voluntarily.'

On 8 November, the British sloop Milford discovered Poncelet shadowing the Anglo-French task force and gave chase. The sloop was too slow to intercept the submarine, so Vice Admiral J. H. D. Cunningham, commander of the 1^st Cruiser Squadron, ordered his flagship, the heavy cruiser Devonshire, to launch its Supermarine Walrus single-engine biplane flying boat. The aeroplane straddled and damaged the submarine with two salvoes of 100-lb (45-kg) depth charges as it attempted to dive, and the boat was then scuttled off Port Gentil. Koenig’s forces landed at Pointe La Mondah on the night of 8 November with forces that included French Legionnaires (including the 13^th Foreign Legion Demi-Brigade) as well as Senegalese and Cameroonian troops.

On 9 November, Westland Lysander army co-operation aircraft operating out of Douala in Free French colours dropped light bombs on the aerodrome of Libreville. The aerodrome was eventually captured despite the stiff resistance met by Koenig’s force as it approached. Free French naval forces, comprising the minesweeper Commandant Dominé and the cargo vessel Casamance, were led by Capitaine de corvette Georges Thierry d’Argenlieu on board the colonial sloop Savorgnan de Brazza in coastal operations. de Brazza attacked and sank her sister ship, Bougainville that was in Vichy French service. Libreville was captured on 10 November.

On 12 November, the last remaining Vichy French forces in Port Gentil surrendered without a fight. Masson committed suicide.

The Free French had lost four aircraft and six aircrew in the campaign, and there is disagreement about the total number of human losses. de Gaulle reported 'some 20 men' died in the campaign, while another writer had claimed that 33 men had been killed. another than 'dozens' had lost their lives, and yet another that about 100 men had lost their lives. Another account states that 35 Vichy French and eight Free French troops had been killed.

On 15 November, de Gaulle made a personal appeal that failed to persuade most of the captured Vichy French soldiers, including Général de Corps d’Armée Marcel Têtu, the vice governor general of French Equatorial Africa, to join the Free French movement. As a result, they were held as prisoners of war at Brazzaville, in French Congo, for the duration of the war.

With their control of French Equatorial Africa consolidated, the Free French began to focus their attentions on the campaign in Italian Libya: de Gaulle switched Leclerc de Hauteclocque from his post in Cameroon and sent him to Fort Lamy in Chad to oversee offensive preparations.

The conflict in Gabon triggered a mass migration of Gabonese civilians to Spanish Guinea. French Equatorial Africa severed its ties with the Vichy French-controlled West African territories, and rebuilt its economy around trade with nearby British possessions, most notably Nigeria. Tensions between Vichy French and Free French factions remained long after the invasion, but the Free French seizure of Gabon and the rest of French Equatorial Africa gave de Gaulle’s movement a new-found legitimacy: no longer was it an organisation of exiles in the UK, for it now had its own sizeable territory to govern.