From the Document: "Iranian military operations in support of the Syrian government since 2011 have exacerbated longstanding tensions between Iran and Israel. These tensions have worsened considerably since late 2016 as Iran has helped Syria's government regain key territory, and in turn has sought a more permanent military presence in Syria. Israeli officials have described the deployment of Iran-backed forces in Syria--particularly in the southwest, near Israel's northern border--as a significant security threat compelling Israeli action. In January 2019, Israeli Prime Minister Binyamin Netanyahu said that Israel had struck Iranian and Hezbollah targets in Syria 'hundreds of times.' In 2018, Israeli and Iranian forces repeatedly targeted one another in and over Syrian- and Israeli-controlled areas. While Israel had conducted numerous air strikes inside Syria since 2012--mostly on targets linked to weapons shipments to Lebanese Hezbollah--the 2018 strikes appeared for the first time to have directly targeted Iranian infrastructure in Syria, and reportedly killed dozens of Iranian personnel. In articulating their 'redlines,' Israeli leaders indicated that Israel would act in Syria to prevent Iran from establishing permanent military bases or weapons factories, and opening new 'terror fronts' against Israel. They also suggested that Israel might attack Iran directly if Iran-backed attacks target major Israeli cities."
CRS In Focus, IF10858
Congressional Research Service: https://crsreports.congress.gov/