Why were the
minutemen so prepared
for the arrival of the
British troops in Concord?

Minutemen were members of well-prepared militia companies of select men from the American colonial partisan militia during the American Revolutionary War. They provided a highly mobile, rapidly deployed force that allowed the colonies to respond immediately to war threats, hence the name.

Explanation:

As early as 1645 in the Massachusetts Bay Colony, some men were selected from the general ranks of town-based "training bands" to be ready for rapid deployment. Men so selected were designated as minutemen. They were usually drawn from settlers of each town, and so it was very common for them to be fighting alongside relatives and friends.

By the time the militia was ready, the British regulars had already captured the arms at Cambridge and Charlestown and returned to Boston. In August 1636, the first offensive military attack by militias failed when Massachusetts sent John Endecott with four companies on an unsuccessful campaign against the Pequot Indians.

The Massachusetts Provincial Congress found that the colony's militia resources were short just before the American Revolutionary War, on October 26, 1774, after observing the British military buildup.

i believe its the indians