All the forces of each side that are engaged in fulfilling the mission of their side are the forces participating in the combat, whether or not they actually shoot or are in harm s way. The three-day Battle of Gettysburg includes a number of separate instances of combat, as does the Battle of the Somme in 1916 and the Battle of the Bulge in 1944. The Battle of Marathon between Greeks and Persians in 490 BC and the naval Battle of Savo Island in 1942 are single instances of combat. We likewise establish no bound as to kind of weapon. Any weapon that is potentially lethal or incapacitating is a candidate.
Weapons can range from fists, knives and clubs to thermonuclear and biological weapons.
The geographical extent and the nature of combat environment are similarly not limited. Combat can occur on land, in the air, at and under the sea, in space, and in any combination of these environments, and it can be confined to a small area or range over a broad expanse in three dimensions. The internal context of combat is all the personnel and materiel of the two opposing sides, together with their mental and physical states, plus the geophysical environment in which combat is waged. Included with these are their physical, psychological, cultural and mental characteristics. The quantity and quality of weaponry are included, and also the mission, the doctrinal and tactical training, and the esprit de corps of troops.