In the days of cannon, it took as long as twenty minutes to load and fire a gun. When a ship fired her guns in salute, she rendered herself powerless for the duration of the reload. By emptying their guns, the ship's crew showed shore batteries and forts that they were no threat. Over time, this gesture became a show of respect, with both shore and ship gun batteries firing volleys.
While many people like to say the 21 gun salute was a tribute to the American Revolution, a number determined as a result of adding together the numbers 1+7+7+6, the truth is the 21 gun salute was an effort to cut costs. The habit of firing salutes became wasteful, with ships and shore batteries firing shots for hours on end. This was particularly expensive for ships, which had a limited space to store powder (which went bad quickly in the salt air). The British admiralty first dictated the policies now in place as a practical matter to save gunpowder. The rule was simple, for every volley fired by a ship in salute, a shore battery could return up to three shots. The regulations limited ships to a total of seven shots in salute, so the 21 gun-salute became the salute used to honor the only the most important dignitaries.
Today, the U.S. Navy Regulations proscribe that only those ships and stations designated by the Secretary of the Navy may fire gun salutes. A national salute of 21 guns is fired on:
- Washington's Birthday
- Memorial Day
- Independence Day
- To honor the President of the United States
- To honor heads of foreign states
Additionally, ships may, with approval from the Office of the Secretary of the Navy, provide gun salutes for naval officers on significant occasions, using the following protocol:
- Admiral - 17 guns
- Vice Admiral - 15 guns
- Rear Admiral (upper half) - 13 guns
- Rear Admiral (lower half) - 11 guns
All gun salutes are fired at five second intervals. Gun salutes will always total an odd number. Capital (large) ships will have two dedicated, special purpose saluting batteries installed onboard for rendering salutes.