Chicago police prevent protesters from placing furniture in front of a bank on May 17, 2012, ahead of the NATO summit in Chicago. (Jim Young / Reuters)
World leaders will gather at the North Atlantic Treaty Organization summit in Chicago, Illinois, on May 20-21, 2012. Thousands of protesters are expected to turn out ahead of and during the meeting to voice their support for various causes.
Chicago has assigned 3,100 officers to the summit to guard against violence, and several other US cities are sending in officers to assist.
The NATO summit follows two days of G8 summit meetings at Camp David in Maryland. - msnbc.com