In order to do this effectively during battle, the military reserve is literally held back in a defensive position, just in case the enemy forces break through the front line. If the enemy makes a mistake or exposes a vulnerable area in their strategy, the military reserve can then be immediately committed to the battle. In some cases, the reserve may provide relief for the troops who are already engaged in fighting – like a second shift line. A military reserve force is quite different, as it can be either composed of part-time military personnel or civilians, all of whom are available to be called upon to fight if there is need for defense against invasion or in order to mobilize against war. Unlike the military reserve, the military reserve force is not counted as part of a country’s permanent body of armed forces.
Since military reserve forces are not actively engaged in battle on a regular basis, other countries legislate that mandatory service in their military can be counted as time spent as a member of the military reserve force. Israel and the Republic of China have a compulsory number of years that each individual must spend as a member of the military reserve force, in addition to completing one’s national service. There is a secondary type of military reserve force that functions slightly differently than the regular reserve forces, and this is known as the Home Guard. The Home Guard – such as the United States National Guard – is a military reserve force that is technically a militia, and can only be called upon to activate in the event of an invasion. The difference is that a Home Guard is composed strictly of civilians who have volunteered for the service, without part-time military personnel involved.