In this English-language story or novel, probably from the 1960s or 70s, the African Americans of Chicago have rebelled against the government. It's part of a general rebellion of black urban populations across the United States. They hole themselves up for months and there are desperate supply problems, vicious fighting, and internal strife, but there is still hope. The Chicago revolutionaries are physically cut off from their worse-off brothers in Gary; they do have contact by radio and eventually are able to fight their way to relieve the smaller city. But when the Chicagoans reach Gary, they find it is empty; instead of people there are huge mass graves. They now realize that the radio messages were faked; they had been allowed to win their way into Gary to demoralize them with a taste of Chicago's future.
This is not Wilson Tucker's The Year of the Quiet Sun (1970).