Thirty years ago this Monday, Argentine marines invaded the Falkland Islands, captured its British defenders and declared the islands to be Argentine territory: Las Malvinas. Britain dispatched a naval "task force" to regain them less than a week later. The Falklands War had begun.

According to newly released documents from the Reagan Library in Simi Valley, Calif., the U.S. almost took sides against its most important ally, driven by the diplomatic maneuvering of Secretary of State Alexander Haig.

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