In April 1942 the Germans began planning to convert De Grasse to a light aircraft carrier, provisionally named II.

On 3 December 1942 Hitler ordered that De Grasse was to be built as an aircraft carrier for Germany but the work was stopped in February 1943 for several reasons, including a lack of materials and manpower and the threat of air attacks in Lorient.

The construction was halted again between 1946 and 1951, when she was towed to the Brest Navy yard to be completed, to a significantly modified design as an anti-aircraft cruiser.

She was used as an anti-aircraft cruiser and flagship within the Mediterranean squadron, until she was selected to join the Pacific Experimentation Centre to participate in the first nuclear tests in French Polynesia.

She undertook some modification in from May 1964 until February 1966, with the bridge being doubled, a 50-meter (160 ft)-high quadripod mast mounted on the aft roof and half the armament removed.