Jean Lafitte – named for the legendary pirate of Barataria, Louisiana, who assisted General Andrew Jackson in defending New Orleans against the British in 1815 – was a C2-S-E1-type merchant ship laid down under a United States Maritime Commission contract (MC hull 475) on 19 April 1942 at Chickasaw, Alabama, by the Gulf Shipbuilding Corporation.

On 1 November 1943, Warren departed Hampton Roads and headed for Panama, reaching the Canal Zone on the 5th after a brief stop at Guantanamo Bay, Cuba, en route.

From 26 November 1943 to 13 January 1944, Warren landed troops of the 4th Marine Division in practice assaults at Aliso Canyon and San Clemente Island.

Her marines were to secure both a guarded passage into the lagoon and artillery bases from which to soften up the defenses on the main islands, Roi and Namur, in support of the landings slated to take place the following day.

However, because of the fierceness of the Japanese resistance on Saipan, Warren's mission was aborted; and she spent over a week cruising off that island, standing by with her Marines forming a reserve force.

She then shifted to the Russell Islands in the Solomons, where she embarked men of the 1st Battalion, 1st Regiment, 1st Marine Brigade – combat veterans of the Guadalcanal campaign.

Despite the carrier-based air strikes and intense bombardment which preceded the initial landings of 15 September, the marines who went ashore that day still met fierce resistance from the Japanese defenders.

The enemy, firmly entrenched in caves and tunnels that honeycombed the hills overlooking the beach and the strategic airfield, proved difficult to dislodge.

Among the first ships to discharge her cargo, Warren remained offshore in the ensuing days, becoming a floating hospital, as doctors and corpsmen worked to sustain lives of men evacuated from "the flaming hell of Peleliu."

On 22 October – two days after the initial landings on Leyte commenced – Warren discharged her cargo and disembarked her troops before pulling out of the area that evening.

Warren returned to Leyte on 14 November, this time with six Red Cross nurses in addition to the Army 1st Battalion, 127th Regiment, 32nd Infantry Division.

The attack transport's commanding officer later recounted, "We all recalled that old superstition of the sea--'women on board ship bring bad luck'--when a Jap torpedo plane came close to hitting us with its deadly charge the afternoon before we sailed into Leyte Gulf."

Only at the last instant a shell from the after 5-inch (130 mm) gun blew the right wing off the "Jill", sending the plane sliding past Warren's fantail and into the sea.

Leyte was still a hot target, so Warren's unloading was efficient and rapid, discharging her cargo within a few hours and getting underway that evening and then slipping away in the darkness, bound for New Guinea.

Accordingly, the destroyer USS Russell (DD-414) and two fast transports moved in close and joined Army heavy artillery in bombarding the area until all opposition was completely silenced.

Ultimately, the attack transport completed one last voyage carrying troops, landing the men of the 1st Battalion, 163rd Regiment, 41st Infantry Division, at Mindoro in the Philippines, after lifting them from Biak Island, New Guinea.

Over the next few days, Warren unloaded the men and material of the 66th Construction Battalion ("Seabees"), undergoing nearly constant air raid alerts as the enemy maintained its pressure on the invading Americans.

There, she embarked the troops of the Army's 43rd Division and headed for Tokyo Bay, reaching that body of water on 13 September, less than two weeks after the formal surrender ceremony on board the battleship USS Missouri (BB-63).

On 16 November, Warren sailed for Manila and participation in the mass movement of men back to the continental United States, Operation Magic Carpet.

After lifting a contingent of seabees to Guam at the end of November, Warren streamed a "homeward bound" pennant on 1 December and set her course for the California coast.

Decommissioned on 14 March 1946, Warren was struck from the Navy list on 17 April 1946 and turned over to the War Shipping Administration on 1 August of the same year at Mobile, Alabama.