Hamas’ attack of Israel on the morning of Oct. 7, 2023, reignited an intractable and bloody conflict in the Middle East that’s been going on for decades.

The militant group – designated a terrorist organization by many countries – invaded from the Gaza Strip and launched rockets at Israeli communities, killing about 1,200 people and taking approximately 200 hostages. The Israeli government subsequently declared war on Hamas, launching aerial assaults on the densely populated strip, which is home to over 2 million Palestinians. More than 11,000 Palestinians reportedly have been killed in Gaza so far, based on figures from the Ministry of Health in Hamas-run Gaza.

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The invasion touched off the latest crisis in a conflict between Israelis and Palestinians that spans well over a century and has been punctuated by periods of violence and shifting land boundaries, but rarely prolonged peace. It’s embroiled other nations in the region and abroad, posing thorny questions centered on respective rights of self-determination.

These are some of the key historical events for understanding the conflict, based on information from the Council on Foreign Relations and the U.N., along with additional sources.