Seventy years after the U.S. dropped the first wartime atomic bomb on Japan, nine nations are estimated to possess a total of around 16,000 nuclear weapons.

This potentially world-ending technology was introduced at exactly 8:15 a.m. Japanese time on the morning of August 6, 1945. A U.S. Air Force B-29 dubbed the Enola Gay flew over the Japanese city of Hiroshima and dropped the bomb code-named “Little Boy.”

Three days later, the U.S. dropped an even larger bomb, “Fat Man,” over Nagasaki. At least 100,000 people were killed instantly across both cities; Japan’s surrender in World War II came within one week.

These events precipitated a seven-decade nuclear arms race. Here’s where things stand today:

How many nuclear weapons are there in the world today?

Most analysts agree there are currently close to 16,000 nuclear weapons in existence, 90 percent of which are owned by the U.S. and Russia. Read more in NBC.