Varying customs among the maritime powers led to confusion in saluting and return of salutes.

The 21-gun salute became the highest honor a nation rendered. When potassium nitrate improved the quality of gunpowder, ships at sea adopted the salute of 21 guns. Early gunpowder, composed mainly of sodium nitrate, spoiled easily at sea, but could be kept cooler and drier in land magazines. The multiple of three probably was chosen because of the mystical significance of the number three in many ancient civilizations.

Land batteries, having a greater supply of gunpowder, were able to fire three guns for every shot fired afloat, hence the salute by shore batteries was 21 guns. The Bible states that God rested on the seventh day after Creation, that every seventh year was sabbatical and that the seven times seventh year ushered in the Jubilee year. Seven planets had been identified and the phases of the moon changed every seven days. Originally warships fired seven-gun salutes-the number seven probably selected because of its astrological and Biblical significance. Since these early devices contained only one projectile, discharging them once rendered them ineffective. The tradition of rendering a salute by cannon originated in the 14th century as firearms and cannons came into use. A North African tribe, for example, trailed the points of their spears on the ground to indicate that they did not mean to be hostile. Apparently this custom was universal, with the specific act varying with time and place, depending on the weapons being used. The use of gun salutes for military occasions is traced to early warriors who demonstrated their peaceful intentions by placing their weapons in a position that rendered them ineffective.

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