The United States has long faced numerous problems when fighting insurgencies. Many of these concern the performance of local allies, who typically play a leading role in counterinsurgency. In this monograph, Dr. Daniel Byman reviews the problems common to the security forces of local allies that have fought or may soon fight insurgencies linked to al-Qa'ida. He argues that these problems stem from deep structural weaknesses, such as the regime's perceived illegitimacy, poor civil-military relations, an undeveloped economy, and discriminatory societies. Together, they greatly inhibit the allied armed forces' effectiveness in fighting the insurgents. Various U.S. programs designed to work with allied security forces, at best, can reduce some of these issues. To be effective, any program to assist allied counterinsurgency forces should factor in the allies' weaknesses. This monograph was written under the Strategic Studies Institute's External Research Associates Program (ERAP).