Um i’m not sure i just answered for the points
The "Red Shirts" are mostly associated with the period that followed after the Reconstruction era of the United States of America. Although they were present from the year 1875 but they became most active after the Reconstruction era. So it can be said that during the late 19th century the "Red Shirts" were most active.
containment was the US' attempt to prevent the spread of communism. they implemented things such as NATO which gave the western countries a defense team against communism, the Marshall plan which helped European countries recover after ww2 which stopped them from being vulnerable enough for the communist countries to take over. (they also used military force as seen in vietnam but its not a policy)
