The Department of Homeland Security asked the Pentagon to accommodate roughly 250 federal agents and 140 vehicles at a military base in Illinois ahead of an expected increase in immigration roundups in the Chicago area, according to an internal government memo obtained by CBS News.

In a request for assistance to the Department of Defense, a top Homeland Security official indicated the Naval Station Great Lakes — the largest military base in Illinois and the Navy's largest training station — would be used as a staging area to oversee "removal operations" in the metropolitan Chicago area targeting immigrants suspected of being in the U.S. illegally.

The memo called for portions of the naval station to be used by Homeland Security agents as a command post and tactical operations cen

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