Biscayne arrived at Mers-el-Kebir, Algeria, on 26 April 1943 and became the flagship of Rear Admiral Richard Lansing Conolly, Commander, Landing Craft and Bases, Northwest African Waters.
While at Mers-el-Kebir she was fitted out as an amphibious force flagship by repair ship USS Delta (AR-9) between 2 and 31 May 1943, although she retained her seaplane tender classification and AVP-11 designation for the time being.
In May 1943, Biscayne shifted her moorings to Bizerte, Tunisia.

Departing Bizerte on 10 July 1943, Biscayne served as flagship of the Joss (Licata) Force in Operation Husky, the Allied invasion of Sicily.
She remained off Sicily until 22 July 1943 and then returned to Bizerte.

Beginning on 9 September 1943, Biscayne took part in Operation Avalanche, the Allied landings at Salerno, Italy, as flagship for Vice Admiral H. Kent Hewitt and Rear Admiral Conolly.
On board the ship during the Anzio invasion was famed journalist Ernie Pyle.
According to Lt.
Earl V. Avery, Admiral Connolly was nicknamed "too close Connolly" by the crew.
One time the admiral wanted to get a closer look at the beach at night and search lights lit them up like a Christmas tree,", according to Avery.
Pyle wrote in his book that a young naval Lieutenant (Avery) remarked "Oh my God, my kids will be orphans."
However, one by one the lights were turned off.
They guessed they were Italian and didn't want to draw their fire.
While off Salerno, she escaped unscathed from frequent air and gunfire attacks.
On 12 September 1943, she sent a fire and rescue team on board the British ammunition ship Lyminge and saved that vessel and her cargo of ammunition from destruction.
Biscayne also served as a temporary hospital ship while off Salerno.
Biscayne retired to Bizerte on 11 October 1943.

On 7 November 1943, Biscayne became the flagship of Rear Admiral F. J. Lowry, Commander, 8th Amphibious Force.
Sailing for Italy once again, she served as flagship during Operation Shingle, the Allied landings at Anzio, from 22 January 1944 to 2 February 1944.

Biscayne became flagship of Rear Admiral B. J. Rodgers, Commander, Amphibious Group 2, 8th Amphibious Force, in May 1944.
Between 15 August 1944 and 16 September 1944, she took part in Operation Dragoon, the Allied invasion of southern France.

On 10 October 1944, Biscayne was officially reclassified as a miscellaneous flagship and redesignated AGC-18.
Biscayne arrived at Mers-el-Kebir, Algeria, on 26 April 1943 and became the flagship of Rear Admiral Richard Lansing Conolly, Commander, Landing Craft and Bases, Northwest African Waters. While at Mers-el-Kebir she was fitted out as an amphibious force flagship by repair ship USS Delta (AR-9) between 2 and 31 May 1943, although she retained her seaplane tender classification and AVP-11 designation for the time being. In May 1943, Biscayne shifted her moorings to Bizerte, Tunisia.
Departing Bizerte on 10 July 1943, Biscayne served as flagship of the Joss (Licata) Force in Operation Husky, the Allied invasion of Sicily. She remained off Sicily until 22 July 1943 and then returned to Bizerte.
Beginning on 9 September 1943, Biscayne took part in Operation Avalanche, the Allied landings at Salerno, Italy, as flagship for Vice Admiral H. Kent Hewitt and Rear Admiral Conolly. On board the ship during the Anzio invasion was famed journalist Ernie Pyle. According to Lt. Earl V. Avery, Admiral Connolly was nicknamed "too close Connolly" by the crew. One time the admiral wanted to get a closer look at the beach at night and search lights lit them up like a Christmas tree,", according to Avery. Pyle wrote in his book that a young naval Lieutenant (Avery) remarked "Oh my God, my kids will be orphans." However, one by one the lights were turned off. They guessed they were Italian and didn't want to draw their fire. While off Salerno, she escaped unscathed from frequent air and gunfire attacks. On 12 September 1943, she sent a fire and rescue team on board the British ammunition ship Lyminge and saved that vessel and her cargo of ammunition from destruction. Biscayne also served as a temporary hospital ship while off Salerno. Biscayne retired to Bizerte on 11 October 1943.
On 7 November 1943, Biscayne became the flagship of Rear Admiral F. J. Lowry, Commander, 8th Amphibious Force. Sailing for Italy once again, she served as flagship during Operation Shingle, the Allied landings at Anzio, from 22 January 1944 to 2 February 1944.
Biscayne became flagship of Rear Admiral B. J. Rodgers, Commander, Amphibious Group 2, 8th Amphibious Force, in May 1944. Between 15 August 1944 and 16 September 1944, she took part in Operation Dragoon, the Allied invasion of southern France.
On 10 October 1944, Biscayne was officially reclassified as a miscellaneous flagship and redesignated AGC-18.
USS Biscayne