By the 17th century, the ordenanças had become the de facto home guard and military reserve force of the Kingdom of Portugal.

Each captaincy was under charge of a captain-major (capitão-mor), appointed by the respective municipal council or, in towns where an alcaide (castle governor) existed, he assumed that role.

Each company was headed by a captain (capitão), assisted by an ensign (alferes), a sergeant, a marshal (meirinho) and a scrivener.

For King Sebastian's Morocco Campaign of 1578, the Ordenanças mobilized 32 companies with a total of around 8000 men, constituting four terços of the Portuguese expeditionary army.

Some of these units acted as guerrilla forces in their respective areas, attacking the rearguard and the logistic lines of the enemy invader armies.

A good example of this was the Peninsular War, where units of Ordenanças constituted a greater part of the garrison of the forts of the Lines of Torres Vedras, including being responsible for manning most of its artillery.