Iran's "axis of resistance" is spread across several Middle Eastern countries and includes Syria as well as Hamas, Hezbollah and other groups that are united in their opposition to Israel and the United States.
Militant groups in Iraq and Yemen's Huthi rebels are also part of the coalition whose attacks on Israel over the past year culminated in Tuesday's missile barrage from Iran.
Here is the history and motivation behind the grouping that has grown in prominence since October 7 last year, when Hamas's deadly attack on Israel triggered the Gaza war.
- Who are they? -