In early 2019, the Islamic Republic of Iran marked its fortieth anniversary, despite decades of isolation, political pressure, sanctions and war. Observers of its security policies continue to try and make sense of this unlikely endurance. Though there are significant disagreements about the Islamic Republic's thinking and intentions, virtually everyone agrees that its policies are fundamentally different from those pursued by their monarchical predecessors. 'No Conquest, No Defeat' offers a historically grounded overview of Iranian national security. Tabatabai argues that Iranian strategic thinking is perhaps best characterised by its dynamic yet resilient nature, one that is continually evolving and whose foundations were laid out decades ago. To understand Iran's national security thinking and policies today, one must examine them in their historical context. As the Islamic Republic enters its fifth decade, this book sheds new light on Iran's controversial nuclear and missile programmes, and its involvement in Afghanistan, Iraq, Lebanon, Syria and Yemen.