Gato Class SubmarineThe first Gato class submarine built was the Drum, which was commissioned on November 1, 1941, the only Gato class submarine to be in service before the attack on Pearl Harbor. She was the first of 73 Gato class submarines ordered in 1940 in response to the realization that the US would probably become involved in the current war. The Gatos were enlarged versions of the Tambor submarine class. They were 350 tons heavier and four feet longer, most of