The two ships searched for German commerce raiders in the early months of the war, and Dunkerque also participated in convoy escort duties.

A 17,500-ton cruiser, which could have handled the Trentos, was inadequate against the old Italian battleships, however, and the 37,000-ton battlecruiser concepts were prohibitively expensive and would jeopardize further naval limitation talks.

She was powered by four Parsons geared steam turbines and six oil-fired Indret boilers, which developed a total of 112,500 shaft horsepower (83,900 kW) and yielded a maximum speed of 29.5 knots (54.6 km/h; 33.9 mph).

Her secondary armament consisted of sixteen 130 mm (5.1 in) /45 dual-purpose guns; these were mounted in three quadruple and two twin turrets.

The 13.2 mm guns were also rearranged slightly, with the two mounts that were located abreast of the second main battery turret moved further aft.

Sea trials were carried out, starting on 18 April 1936, at which time her superstructure was not yet complete, and many of her secondary and anti-aircraft guns had not been installed.

VA François Darlan, the Chief of the Naval General Staff, came aboard on 3 March to observe further gunnery tests.

In early 1938, the crew prepared the ship for her first major cruise to test her ability to operate at extended ranges, which began on 20 January.

Dunkerque departed Brest on 8 November in company with Béarn and the 4th Cruiser Division for a visit to Cherbourg to celebrate the twentieth anniversary of the Armistice with Germany that ended World War I.

[16] The next day, Dunkerque sortied to take part in maneuvers with the Atlantic Squadron off the Brittany coast; another stint in the shipyard for repairs followed from 17 March to 3 April.

[17] In response to the Sudetenland Crisis over Nazi Germany's demand to annex the Sudetenland region of Czechoslovakia, the French naval command sent elements of the Atlantic Squadron, including Dunkerque, three light cruisers, and eight large destroyers, on 14 April to cover the training cruiser Jeanne d'Arc as it returned from a cruise to the French West Indies; at the time, a German squadron centered on the large heavy cruiser Admiral Graf Spee was off the coast of Spain.

On 1 May, Strasbourg joined Dunkerque for the first time for a cruise to Lisbon, Portugal on 1 May, arriving there two days later for a celebration of the anniversary of Pedro Álvares Cabral's discovery of Brazil.

[21] In August, as tensions with Germany were again heightened, this time over territorial demands on Poland, the French and British navies discussed coordination in the event of war with Germany; they agreed that the French would be responsible for covering Allied shipping south from the English Channel to the Gulf of Guinea in central Africa.

British observers informed the French Navy that the German "pocket battleships" of the Deutschland class had gone to sea in late August, bound for the Atlantic, and that contact with the vessels had been lost.

On 2 September, the day after Germany invaded Poland, but before France and Britain declared war, the Force de Raid sortied from Brest to guard against a possible attack by the Deutschlands.

On 22 October, Dunkerque and two cruisers sortied with their destroyer screen to cover Convoy KJ 3 to Kingston, Jamaica, arriving back in Brest three days later.

While cruising off Iceland, Dunkerque ran into very heavy seas; her bow was repeatedly submerged by the large waves, and she had to slow to 10 knots (19 km/h; 12 mph) to avoid damage.

[26] On 11 December, Dunkerque and the cruiser Gloire carried a shipment of part of the Banque de France's gold reserve to Canada.

[26] Faced with increasingly hostile posturing by Italy during the spring of 1940, the Force de Raid was dispatched to Mers-el-Kébir on 2 April.

The French had received faulty intelligence that had indicated that the Germans would attempt to force a group of battleships through the Strait of Gibraltar to strengthen the Italian fleet.

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.

It also defeated the belt and the torpedo bulkhead and then exploded in boiler room 2, causing extensive damage to the propulsion machinery.

Gensoul expected that the ship would be ready to sail for Toulon for permanent repairs within a few days and informed his superior, Admiral Jean-Pierre Esteva (Amiral Sud, the commander of naval forces in North Africa) as much.

Three patrol boats were moored alongside to evacuate the remaining crew aboard in the event of another attack, and these vessels were loaded with depth charges.

The first wave scored a hit on the patrol boat Terre-Neuve, and though it failed to explode, the hole it punched in her hull caused her to sink in the shallow water.

Dunkerque was finally ready to cross the Mediterranean on 19 February; she got underway at 04:00, escorted by the destroyers Vauquelin, Tartu, Kersaint, Frondeur, and Fougueux.

Dunkerque reached Toulon at 23:00 on 20 February; her crew was reduced to comply with the terms of the armistice on 1 March, and on 22 June, she entered the large Vauban dock for permanent repairs.

To prevent them from seizing the ships, their crews scuttled the fleet in Toulon, including Dunkerque, which still lay incomplete in the Vauban drydock.

Since she was in the far side of the dockyard, it took the Germans over an hour to reach the vessel, and in the confusion, they made no attempt to close the locks.

[48] As part of this process, the ship was deliberately damaged to prevent the French from being able to repair her if she was recaptured; the Italians cut down the main battery guns to render them unusable.