After early peacetime training activity, and two fruitless missions in the Mediterranean Sea, the Barbarigo was assigned to the Atlantic theater, reaching its base in Bordeaux on 8 September 1940, after an unsuccessful patrol.

With he and his crew being convinced they had seen and felt the "battleship" being struck and sinking, Barbarigo sailed away, while the American ships had not even been aware of the attack.

Again, Grossi's "success" was widely reported, and he was promoted to Capitano di Vascello (Captain) and awarded a second Gold Medal; he left the submarine to replace Polacchini as BETASOM commander.

After the war, Grossi's actions would be the object of two enquiries in 1949 and 1962, which concluded that he and his crew had been in good faith, but stripped him of his promotions and awards.

After a period of time for repairs, as well as some replacements and retraining of crew, the submarine was converted into a transport to carry materiel between Germany and Japan in 1943, with guns, torpedoes and all but one periscope being removed; it departed Bordeaux on 16 June, with 130 tons of valuable load, but disappeared.