Do you use an article with the word of army?

You generally don't use an article ("a", "an", or "the") with the word "army" when it refers to a general concept of a military force. For example:

* Army is a powerful force.

* Army training is rigorous.

However, you do use an article when "army" refers to a specific army:

* The army of the United States is large and well-equipped.

* He joined the army after graduating high school.

Here's a breakdown:

No article:

* Army as a general concept

* Army as a noun of material (referring to the soldiers themselves)

* Army as a collective noun (referring to the group as a whole)

Article used:

* The army when referring to a specific army (e.g., the British Army, the Army of the United States)

* An army when referring to a single, specific army (e.g., "An army of ants marched across the lawn.")

Remember, the context will always determine whether or not an article is needed.