The key evidence of U.S. deception was this:
On the evening of Oct. 24, 1983, two messages were sent by Washington, hours after a British minister had told Parliament that there was no indication of an imminent American invasion. The first message said that the United States was considering a request from some Caribbean nations to intervene; the second, sent within four hours, said that it had decided to go ahead.As the official JCS history of the intervention, called Operation Urgent Fury, details, President Reagan's decision to authorize the execute order was made on October 22, two days before the deceptive messages to Britain, which were sent only hours before the military invasion began.
The British wrongly believed, however, that the action had been planned "for some time." In fact, a military coup and the death of the Grenadian prime minister on October 13 prompted planning for a noncombatant evacuation of American medical students because of the unrest. Only on October 20 did a senior leadership group decide that the military mission might need to be expanded to include "neutralization of Grenadian forces and armed Cuban workers" as well as establishment of a new government for the island.
While "Urgent Fury" succeeded in evacuating grateful American students, it exposed huge problems in U.S. military planning and operations which accelerated momentum for military reform legislation that became the Goldwater-Nichols law in 1986. Lawmakers learned, for example, that one officer had to make a crucial call for assistance on a pay phone with his credit card because of a lack of interoperable radios among the combined military units.