Here’s how the scheme worked: The RNC mailed these voters letters in envelopes marked, “Do not forward”, to be returned to the sender. These letters were mailed to servicemen and women, some stationed overseas, to their US home addresses. The letters then returned to the Bush-Cheney campaign as “undeliverable.”
The lists of soldiers of “undeliverable” letters were transmitted from state headquarters, in this case Florida, to the RNC in Washington. The party could then challenge the voters’ registration and thereby prevent their absentee ballots being counted.
It was an attempt to use African Americans' service to their country to rob them of their right to vote. Tim Griffin, one of Rove's flying monkeys, allegedly led such a caging effort in '04. He's now the U.S. Attorney for the state of Arkansas.