With the outbreak of war in September, "Suffren" patrolled the South China seas on the lookout for German merchantmen. In November she went to Singapore to aid in the escort of an Australian troop convoy to Colombo. She continued to escort convoys in the Indian Ocean until the end of April 1940. On 18 May 1940 she arrived at Alexandria to join Vice Admiral Godfroy's Force X. She sailed in concert with cruiser and fleet torpedo boat arriving in Beirut on 21 May, joined by "Duquesne" and six days later. Two more fleet torpedo boats and arrived on 24 and 25 May respectively. On 11 June the ships conducted a raid into the Aegean Sea off Crete, finding nothing returned to Alexandria on 13 May. On 21 June she sailed with "Duguay-Trouin" in response to a report of three Italian cruisers moored at Tobruk. Finding no vessels in the port they returned to Alexandria that evening. On 22 June the official notification of the French Armistice with Germany was delivered. All French ships were barred from departing the harbour after 23 June. On 3 July Vice-Admiral Cunningham presented Vice Admiral Godfroy the ultimatum - surrender the ships to British control, demilitarize the ships at their moorings or scuttle. The admirals signed an agreement on 7 July to demilitarize the vessels.