A more thorough explanation:

A commission of lieutenancy was a document issued to appoint officers to establish military order over the inhabitants of a county. This replaced the commission of array which had similar powers. The commission of lieutenancy became obsolete with the establishment of the militia system.

During the 16th and 17th centuries, commissions of lieutenancy were issued in England to maintain order and security in the counties. The appointed officers were responsible for organizing and leading the local militia, as well as enforcing laws and regulations.

For example, during the English Civil War, commissions of lieutenancy were used to raise troops and maintain order in the counties. The appointed officers were responsible for recruiting soldiers, training them, and leading them into battle.

Another example is during the Napoleonic Wars, when commissions of lieutenancy were used to organize the local militia and defend against possible French invasion.

These examples illustrate how commissions of lieutenancy were used to establish military order and maintain security in the counties.