Standing army

A permanent, regularly organized military force maintained by a state in peacetime. Unlike a militia or wartime levy, it remains in service between conflicts.

Military logistics: The planning and delivery of personnel, equipment, food, and services to armed forces. Regular supply systems keep soldiers and equipment ready outside active campaigns.
Ancient Rome: The civilization centered on Rome that developed into a republic and later an empire. Roman armies illustrate how a state could maintain organized forces across long periods.
Fiscal-military state: A state whose tax and administrative systems are organized substantially around financing warfare and armed forces. Standing armies helped drive the recurring revenue systems characteristic of this form of government.
Militia: A military force composed of civilians who serve part-time or are called up for emergencies. A militia is typically activated as needed rather than maintained as a full-time force.
Military deterrence: A strategy of discouraging hostile action by threatening unacceptable costs or denying an opponent's objectives. A ready force can make potential aggression appear costly before fighting begins.
Military rank: A hierarchical system that establishes authority and responsibilities within armed forces. Ranks make command relationships durable across units and peacetime duties.
Roman legion: The principal organized infantry formation of the Roman army, whose size and structure changed over time. Legions show the durable unit structure behind Rome's military institutions.
Taxation: The compulsory financial contributions governments collect from people and businesses. Maintaining troops in peacetime required revenue collected on a continuing basis.
Conscription army: An army whose personnel are recruited primarily through compulsory military service. Recruitment by conscription differs from the defining feature of permanent peacetime organization.
Collective defense: An arrangement in which members of an alliance treat an attack on one as a concern for all. Standing forces give alliances capabilities they can deploy without first building an army from scratch.

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