Once again, the British can be credited with creating a military tradition.
All salutes are signals for voluntary submission.
Prior to the invention of firearms early use of the salute was first employed by ships that were coming to shore and wanted to show that they meant no harm by discharging their cannon seven times. After this warning practice caught on cannons on land would return the salute by firing three shots for every shot the ships discharged.
Another custom involving the gun salute originated from the European Dynastic Wars (1688-1748) in which the fighting would be partially stopped so that the dead and wounded could be removed from the field of battle. After that was accomplished three shots were fired into the air to signal that the fighting could resume.
Sometime between 1688 and 1730 the British Royal Navy regulated the number of guns to be used in saluting different ranks. For the Prime Minister 19 guns should be used but for royalty or heads of state the salute should be done with 21 guns. (Same for Donald Trump or Joe Biden.)
In America military and police funerals, an Honor Guard of seven members of the rifle party will fire blank cartridges into the air three times from a safe distance.
Ironically Irish Republicans also fire a three-volley salute at the funerals of IRA (Irish Republican Army) and INCA (Irish National Libertarian Army) Volunteers!
(Excerpts from “The Little Book of Answers” – Author – Doug Lennox – (2003) – MJF Books – New York, NY 1001.)