Nation: STALAG '68

ON the site of Chicago's International Amphitheatre, all manholes have been sealed with tar. A chain-link fence, seven feet high and topped with barbed wire, is going into place west of the arena. Secret Service men are checking every pipe, seat and rafter against bombs or snipers' hiding places. Taking antiwar demonstrators at their word, Chicago officials are preparing for every possible disruption at next week's Democratic National Convention. In the process, the nation's second largest city is beginning to take on the appearance of a city under siege.

Protest groups hope to muster at least 100,000 marchers outside the amphitheatre the...