When Hamas militants led a deadly cross-border raid on Oct. 7, 2023, they triggered a war with Israel that has devastated Gaza. They also set off shock waves that have reshaped the Middle East in unexpected ways.

Powerful alliances were upended. Long-established “red lines” were crossed. A decades-old dictatorship at the heart of the region was swept away.

Fifteen months after the October attacks, with a cease-fire deal between Israel and Hamas set to start on Sunday, here is a look at how the region has been radically transformed.

Israel

Israel has reasserted its military dominance but may face heavy diplomatic and domestic costs.

The country’s leaders treated the Hamas-led attacks as an existential threat and have been determined to defeat Hamas and weaken its main backer, Iran. Israel has not only succeeded in debilitating Hamas in Gaza, but has also decimated the Lebanese Shiite group Hezbollah and dealt a heavy blow to Iran’s network of Middle Eastern allies.