Salutes may be fired with personal weapons, field pieces, or ship’s cannons. The origins of such salutes are a little obscure. Making a loud noise has long been regarded as a form of celebration. Another suggestion is that the salute was originally a sign of trust, originating around the 14th century. In the days of muzzle-loading cannons, it took a while to reload a ship’s armament once it had been fired. So when a ship was approaching a foreign port or another friendly ship, all the cannons on board would be fired to show that they were empty and posed no threat. It was also a sign of trust that people on land or in the other vessel not to open fire on them. In time, this practice was adopted as a way to honour dignitaries on land as well.
The salute today is not fired in one large burst of gunfire but rather as a rolling volley, in which one gun fires after another. It’s said that this practice originated in less chivalrous, more pragmatic times. By firing one gun after another, a symbolic salute could be fired to honour a VIP, but some guns would remain loaded so as not to leave the vessel wholly defenceless. A specific number of guns is fired to honour VIPs in accordance with their status. Royalty and heads of state receive a 21-gun salute, field marshals, state officials and equivalents receive a 19-gun salute, generals and equivalent ranks receive 17, and so on down to 11 for a brigadier.