The USS Indianapolis, a Portland-class heavy cruiser of the United States Navy, embarked on a secret mission from San Francisco to Tinian Island in July 1945. This journey was crucial for the wartime effort, as it involved transporting key components for the atomic bomb called 'Little Boy,' which was designed to be dropped on Japan. The ship was loaded with uranium enrichment and bomb casing components that were critical for the successful detonation of the bomb. The Indianapolis left San Francisco on July 16 with little fanfare and was under strict orders to maintain secrecy around its cargo.

Tinian, part of the Mariana Islands group in the Pacific, was a pivotal staging ground for operations against Japan. The decision to use Tinian as a base was influenced by its strategic location and the island's infrastructure, which facilitated the logistical needs of the atomic bomb mission. Upon arriving at Tinian, the components were handed over to the 509th Composite Group, the unit responsible for the bomber operations that would ultimately lead to the deployments over Hiroshima and Nagasaki.

The successful delivery of the bomb parts was integral to the culmination of the Manhattan Project, a top-secret initiative that aimed to develop nuclear weapons before Nazi Germany could achieve similar capabilities. The mission of the USS Indianapolis has been remembered for its historical significance, leading to profound changes in warfare, international relations, and the moral conversations surrounding the use of atomic energy.