This report analyzes the U.S. and allied campaign against the al Qa’ida–linked terrorist group al Shabaab in Somalia, examines what steps have been most successful against the group, and identifies potential recommendations. It concludes that, while al Shabaab was weakened between 2011 and 2016, the group could resurge if urgent steps are not taken to address the political, economic, and governance challenges at the heart of the conflict. This study finds that a tailored engagement strategy — which involved deploying a small number of U.S. special operations forces to conduct targeted strikes, provide intelligence, and build the capacity of local partner forces to conduct ground operations — was key in degrading al Shabaab. Still, progress in Somalia is reversible in the absence of continued and consistent pressure and political, economic, and social reforms. Today’s terrorism and insurgency landscape defies easy solutions, with challenges from the Islamic State, al Qa’ida, and other groups across the Middle East, Europe, Asia, and Africa. While there has been a significant focus on how and why the U.S. and other Western governments have failed to degrade terrorists and insurgents in Iraq, Syria, Afghanistan, Libya, and other countries, there has been far less attention on successful efforts to degrade groups. In Somalia, there has been limited progress. The challenge will be preventing a reversal….