The contradictory trends of the ‘post-Arab Spring’ landscape form both the backdrop to, and the focus of, this volume on the changing security dynamics of the Persian Gulf, defined as the six GCC states plus Iraq and Iran. The political and economic upheaval triggered by the uprisings of 2011, and the rapid emergence of the Islamic State of Iraq and Syria in 2014, have underscored the vulnerability of regional states to an intersection of domestic pressures and external shocks. The initial phase of the uprisings has given way to a series of messy and uncertain transitions that have left societies deeply fractured and ignited violence both within and across states. The bulk of the protests, with the notаble exception of Bahrain, occurred outside the Gulf region, but Persian Gulf states were at the forefront of the political, economic, and security response across the Middle East. This volume provides a timely and comparative study of how security in the Persian Gulf has evolved and adapted to the growing uncertainty of the post-2011 regional landscape.