Not accommodating terrorists seems like an obvious lesson, but when you live in the Middle East, where governments like Iran and Syria have supported terrorism and groups like Hamas and Hezbollah controlled territory, working with extremist groups and their supporters seems like a necessary evil. Before Oct. 7, Israel relied on a mix of coercion and inducements to manage Hamas, convinced that material incentives and pressure had created a pragmatic governing partner in Gaza. In Lebanon, Israel focused mostly on deterrence to counter Hezbollah, using the threat of punishment to dissuade the group from launching attacks. Oct. 7 shattered the assumption that you could manage terrorists, reinforcing Prime Minister Benjamin Netanyahu’s refusal to negotiate with Hamas and driving all-out campaigns against Hezbollah, Iran, and military targets in Syria.

The Oct. 7, 2023, terrorist attacks on Israel were a strategic shock of historic proportions. As with other cataclysmic events like 9/11, they generated immediate lessons on the dangers of terrorism, the challenges facing intelligence services , and the costs of complacency. Israeli leaders, reeling from the trauma, launched wide-ranging operations not only in Gaza but also against targets in Iran, Lebanon, Syria, the West Bank, and Yemen. For many Israelis, Oct. 7 seemed to confirm hard truths about the nature of their enemies and the perfidiousness of supposed friends. Yet in practice, these lessons were only partially correct—and in several cases dangerously incomplete.

The Oct.