Domestic terrorism is committed by homegrown groups who have no ties or connections outside the United States. International terrorists' activities transcend national boundaries or are sponsored by international groups. The FBI's primary goal in conducting counterterrorism investigations is to prevent a terrorist incident from occurring. From 1983 to 1987, the FBI was successful in preventing more than 45 terrorist incidents in the United States. Even so, almost every major Middle East terrorist organization has a surrogate structure in the United States. Most terrorist incidents in the United States, however, are committed by domestic groups, including the Aryan Nations; the Covenant, the Sword, and the Arm of the Lord; the Sheriff's Posse Comitatus; and Puerto Rican groups which seek to achieve independence for Puerto Rico.