US Army via Hiroshima Peace Memorial Museum
A mushroom cloud billows into the sky about an hour after an atomic bomb was dropped on Hiroshima, Japan.
The Enola Gay, a B-29 Superfortress bomber, deployed the most powerful weapon then known to man over Hiroshima.
The southern Japanese city was "an important army depot and port of embarkation," but its location and population also appealed to US officials who wanted to showcase their new weapon's destructive power.
Sunday marks the 72nd anniversary of the bombing of Hiroshima, ordered by President Harry Truman in the final days of the war.
In 2016, just a few months before the 71st anniversary, then-President Barack Obama became the first sitting president to visit the city - a trip to, in his words, "ponder a terrible force unleashed in a not-so-distant past."
President Donald Trump, then a candidate for the presidency, was critical of Obama's remarks.
YouTube/Amanda Macias/Business Insider
Bird's-eye-view footage of the "Little Boy" attack.
The 5-ton nuclear bomb, named "Little Boy," emerged from the Einstein-inspired Manhattan Project. The Enola Gay released it some 30,000 feet above the city, and the bomb fell for 44.4 seconds before detonating in a blast that would ultimately kill 140,000 people and destroy 90% of the city.
Three days later, the US dropped another bomb farther south, on the Japanese city of Nagasaki. That blast killed about 40,000 people instantly - thousands more would die of radiation poisoning.
Japan announced its surrender to Allied forces on August 15. On September 2, Japanese leaders signed the formal instrument of surrender aboard the USS Missouri, anchored in Tokyo Bay, formally ending World War II.
AP
A huge expanse of ruins left from the explosion of the atomic bomb on August 6, 1945, in Hiroshima.
Amanda Macias composed an earlier version of this post