Levy is a research technology in Age of Empires III. It rapidly musters six Minutemen (in five seconds) to defend the Town Center from enemy attack.
Available only to European civilizations, such as the British, the technology costs 150 
and 150 
and can be used only once. With the Colonial Militia Home City Card, however, Levy can be researched one more time.
Minutemen
Minutemen are a good tool for quickly defending the colony if rushed by opponents. They are also effective in large infantry armies due to their good attack and being protected by the numbers around them.
This is especially true of the Portuguese because of their free multiple Town Centers. By the Industrial Age, it is possible to have up to twenty Minutemen included in an army for low cost.
But the fact that they automatically lose hit points should be kept in mind: they should not attack distant areas, as they arrive at such locations drained of hit points.