The only test in battle for Dunkerque came in the attack on Mers-el-Kébir on 3 July.
The British, misinterpreting the terms of the armistice as providing the Germans with access to the French fleet, feared that the ships would be seized and pressed into service against them despite assurances from Darlan that if the Germans attempted to take the vessels, their crews would scuttle them.
Prime Minister Winston Churchill then convinced the War Cabinet that the fleet must be neutralized or forced to re-join the war on the side of Britain.
The British Force H, commanded by Admiral James Somerville and centered on HMS Hood and the battleships Resolution, and Valiant, arrived off Mers-el-Kébir to coerce the French battleship squadron to join the British cause or scuttle their ships.
The French Navy refused, as complying with the demand would have violated the armistice signed with Germany.
To ensure the ships would not fall into Axis hands, the British warships opened fire at 17:55.
Dunkerque was tied alongside the mole with her stern facing the sea, so she could not return fire.

Dunkerque's crew loosed the chains and started to get the ship underway just as the British opened fire; the ship was engaged by HMS Hood.
The French gunners responded quickly and Dunkerque fired several salvos at Hood before being hit by four 15-inch (381 mm) shells in quick succession.
The first was deflected on the upper main battery turret roof above the right-most gun, though it shoved in the armor plate and ignited propellant charges in the right turret half that asphyxiated all the men in that half; the left half remained operational.
The shell itself was deflected off the turret face and failed to explode when it landed around 2,000 m (6,600 ft) away.
Fragments of armor plate that had been dislodged by the impact destroyed the run-out cylinder for the right gun, disabling it.
The second shell passed through the unarmored stern, penetrating the armor deck and exiting the hull without exploding.
Though it did little damage, the shell did cut the control line for the rudder, forcing the ship to use manual control, which hampered the crew's ability to steer the ship as they attempted to get underway.

The third shell hit the ship shortly after 18:00; this projectile struck the upper edge of the belt on the starboard side; since the belt had only been designed to defeat German 28 cm (11 in) shells, the much more powerful British shell easily perforated it.
The shell then passed through the handling room for the starboard secondary turret No.
III, igniting propellant charges and detonating a pair of 130 mm shells as it did so.
The 15 in round then penetrated an internal bulkhead and exploded in the medical storage room.
The blast caused extensive internal damage, allowing smoke from the ammunition fire to enter the machinery spaces, which had to be abandoned, though debris from the explosion had jammed the armored doors shut.
Only a dozen men were able to escape using a ladder at the forward end of the room.
The fourth shell struck the belt aft of the third hit and at the waterline.
It also defeated the belt and the torpedo bulkhead and then exploded in boiler room 2, causing extensive damage to the propulsion machinery.
Dunkerque rapidly lost speed and then all electrical power; unable to get underway or further resist the British ships, Dunkerque was beached on the other side of Mers-el-Kébir roadstead to prevent her from being sunk.

The British fire ceased after less than twenty minutes, which limited the damage inflicted; Somerville hoped to minimize the damage done to Franco-British relations.
Work on the ship began almost immediately; at 20:00, Gensoul ordered the crew to recover the dead and wounded while damage control teams stabilized the ship.
Those not engaged in either work—some 800 men—were sent ashore.
Half an hour later, he radioed Somerville that the ship had been largely evacuated.
By the next morning, the fires had been suppressed and work to plate over the shell holes in the hull had begun.
Wounded crewmen had been evacuated to a lo
The only test in battle for Dunkerque came in the attack on Mers-el-Kébir on 3 July. The British, misinterpreting the terms of the armistice as providing the Germans with access to the French fleet, feared that the ships would be seized and pressed into service against them despite assurances from Darlan that if the Germans attempted to take the vessels, their crews would scuttle them. Prime Minister Winston Churchill then convinced the War Cabinet that the fleet must be neutralized or forced to re-join the war on the side of Britain. The British Force H, commanded by Admiral James Somerville and centered on HMS Hood and the battleships Resolution, and Valiant, arrived off Mers-el-Kébir to coerce the French battleship squadron to join the British cause or scuttle their ships. The French Navy refused, as complying with the demand would have violated the armistice signed with Germany. To ensure the ships would not fall into Axis hands, the British warships opened fire at 17:55. Dunkerque was tied alongside the mole with her stern facing the sea, so she could not return fire.
Dunkerque's crew loosed the chains and started to get the ship underway just as the British opened fire; the ship was engaged by HMS Hood. The French gunners responded quickly and Dunkerque fired several salvos at Hood before being hit by four 15-inch (381 mm) shells in quick succession. The first was deflected on the upper main battery turret roof above the right-most gun, though it shoved in the armor plate and ignited propellant charges in the right turret half that asphyxiated all the men in that half; the left half remained operational. The shell itself was deflected off the turret face and failed to explode when it landed around 2,000 m (6,600 ft) away. Fragments of armor plate that had been dislodged by the impact destroyed the run-out cylinder for the right gun, disabling it. The second shell passed through the unarmored stern, penetrating the armor deck and exiting the hull without exploding. Though it did little damage, the shell did cut the control line for the rudder, forcing the ship to use manual control, which hampered the crew's ability to steer the ship as they attempted to get underway.
The third shell hit the ship shortly after 18:00; this projectile struck the upper edge of the belt on the starboard side; since the belt had only been designed to defeat German 28 cm (11 in) shells, the much more powerful British shell easily perforated it. The shell then passed through the handling room for the starboard secondary turret No. III, igniting propellant charges and detonating a pair of 130 mm shells as it did so. The 15 in round then penetrated an internal bulkhead and exploded in the medical storage room. The blast caused extensive internal damage, allowing smoke from the ammunition fire to enter the machinery spaces, which had to be abandoned, though debris from the explosion had jammed the armored doors shut. Only a dozen men were able to escape using a ladder at the forward end of the room. The fourth shell struck the belt aft of the third hit and at the waterline. It also defeated the belt and the torpedo bulkhead and then exploded in boiler room 2, causing extensive damage to the propulsion machinery. Dunkerque rapidly lost speed and then all electrical power; unable to get underway or further resist the British ships, Dunkerque was beached on the other side of Mers-el-Kébir roadstead to prevent her from being sunk.
The British fire ceased after less than twenty minutes, which limited the damage inflicted; Somerville hoped to minimize the damage done to Franco-British relations. Work on the ship began almost immediately; at 20:00, Gensoul ordered the crew to recover the dead and wounded while damage control teams stabilized the ship. Those not engaged in either work—some 800 men—were sent ashore. Half an hour later, he radioed Somerville that the ship had been largely evacuated. By the next morning, the fires had been suppressed and work to plate over the shell holes in the hull had begun. Wounded crewmen had been evacuated to a lo
French battleship Dunkerque