An invasion force was sent to land at Anzio to attack the rear of the German's right flank. The landings seemed to take the German's by surprise. The beachhead was firmly established by the time Nazi reinforcements began to pour into the area. The major entrance for the German's was the bridge over the Mussolini Canal. To keep the Nazi's from reinforcing their infantry units, Naval gunfire was necessary. One of the first destroyers to give assistance at Anzio was the USS Mayo, commanded by Commander Kaplan. On D-Day, she steamed in to bombard enemy positions on the Anzio beachhead. On January 23, she was still at it; sending a continuous barrage of gunfire wherever needed. By this time, the German's had moved artillery pieces up to the Anzio beaches and were fighting their way across the bridge at Mussolini Canal. Again the American landings were being pushed into the sea.

Mayo, seeing the imminent danger of a German counterattack, shifted her 5in guns toward the bridge and halted German troop movements across the Mussolini Canal. Admiral Lowry documents the results of the Mayo's action as follows:

Another danger was a railroad gun called "Anzio Annie" that was stored in a tunnel above the beach. Unleashed, this gun could wipe out artillery, armored vehicles, and the troops themselves. Every now and then this gun would come out and pummel the troops with its high caliber gun. Mayo was detached to keep "Annie" at bay by firing a shell at the tunnel about every 5 minutes during the peak of battle. This kept the German's from risking the big gun to naval gunfire.

Mayo continued to shell Nazi targets until the evening of January 24, when it is believed that she hit a mine. The explosion created a huge gaping hole in her starboard side, wrecking and flooding the After-engineroom and Fireroom, rupturing the bulkheads between the two compartments, bulging the main deck, and bending the starboard propeller shaft. With the loss of 6 men killed, one missing, and 25 wounded, the crew desperately battled to save the ship. Though almost broken in two, the Mayo was kept above water and towed to Naples for temporary repairs. The USS Mayo went stateside for permanent repairs and modernization.

Mayo in dry-dock after Anzio explosion

The U.S.S. Mayo earned her second battle star and her Captain received the Letter of Commendation Ribbon for outstanding action off the coast of Anzio.