The Association for Diplomatic Studies and Training just posted an oral history titled "When the Sudanese Autocrat Met President Reagan and Lost His Job" with William Pierce, U.S. embassy Khartoum political officer at the time.
This is a first hand account of the overthrow in 1985 of Sudanese President Gaafar Nimeiry while he was in the United States on a visit with President Ronald Reagan. William Pierce offers background to this development.