Iran has spent decades building multi-tiered military capabilities at home and across the region that were at least partly aimed at deterring the United States from attacking it.

European nations worked Monday to keep alive diplomatic efforts to curb the Israel-Iran war as the two countries traded strikes following the United States’ weekend attack on Iran’s nuclear program.

The National Terrorism Advisory System issued a bulletin warning about the threat of retaliatory actions due to the U.S. military strikes against Iran, including hate crimes by violent extremists against perceived Jewish or pro-Israel targets and Iranian state-backed cyberattacks.