What does the National Guard do? Why are its troops in US cities?

"The National Guard is a state-based military force whose troops wear uniforms and rank, operate military vehicles and weapons, and have often been called upon to serve alongside regular active-duty units in war. But when deployed domestically, the guard has traditionally been asked to provide humanitarian assistance, not to act as a partisan strike force at the whim of the president."

"Tracing its history to the Massachusetts militia in 1636, the National Guard is a component of the U.S. military that has state and federal missions and traditionally operates under the jurisdiction of governors under Title 32 of the U.S. Code. By comparison, the active-duty military operates under Title 10 of the U.S. Code, and the 1878 Posse Comitatus Act makes it a crime to use the regular military as a domestic police force in most circumstances."

The National Guard traces roots to the 1636 Massachusetts militia and serves both state and federal missions, traditionally operating under governors' jurisdiction under Title 32. The active-duty military operates under Title 10, and the Posse Comitatus Act generally bars using the regular military as domestic police. Domestically, the guard is typically deployed for humanitarian assistance rather than partisan policing, though troops wear uniforms and use military vehicles and weapons. President Trump has federally mobilized the guard several times this year in Democratic-led cities for crime and immigration enforcement. Congress elevated the National Guard Bureau chief to a four-star position and added the role to the Joint Chiefs; the current chief is Gen. Steven S. Nordhaus.

Read at Boston.com