. In such countries, the word "army" on its own retains its connotation of a land force in common usage. The current largest army in the world, by number of active troops, is the People's Liberation Army

People's Liberation Army

The People's Liberation Army is the unified military organization of all land, sea, strategic missile and air forces of the People's Republic of China. The PLA was established on August 1, 1927 — celebrated annually as "PLA Day" — as the military arm of the Communist Party of China...

 of China

People's Republic of China

China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

 with 2,250,000 active troops and 800,000 reserve personnel

Military reserve force

A military reserve force is a military organization composed of citizens of a country who combine a military role or career with a civilian career. They are not normally kept under arms and their main role is to be available to fight when a nation mobilizes for total war or to defend against invasion...

 followed by the Indian Army

Indian Army

The Indian Army is the land based branch and the largest component of the Indian Armed Forces. With about 1,100,000 soldiers in active service and about 1,150,000 reserve troops, the Indian Army is the world's largest standing volunteer army...

 with 1,325,000 active troops and 2,142,821 reserve personnel.

By definition, irregular military

Irregular military

Irregular military refers to any non-standard military. Being defined by exclusion, there is significant variance in what comes under the term. It can refer to the type of military organization, or to the type of tactics used....

 is understood in contrast to regular armies

Regular army

A regular army consists of the permanent force of a country's army that is maintained under arms during peacetime.Countries that use the term include:*Australian Army*British Army*Canadian Forces, specifically "Regular Force"*Egyptian army*Indian Army...

 which grew slowly from personal bodyguards or elite militia

Militia

The term militia is commonly used today to refer to a military force composed of ordinary citizens to provide defense, emergency law enforcement, or paramilitary service, in times of emergency without being paid a regular salary or committed to a fixed term of service. It is a polyseme with...

.
The Spartan Army

Spartan Army

The Spartan army was the military force of Sparta, one of the leading city-states of ancient Greece. The army stood at the centre of the Spartan state, whose citizens' primary obligation was to be good soldiers. Subject to military drill from infancy, the Spartans were one of the most feared...

 was one of the earliest known professional armies.