The US and the UK (and other coalition partners) are assisting the predominantly Kurdish Syrian Democratic Forces with the destruction of Daesh in Syria.
They have also used ship launched missiles and air strikes against Syrian Government facilities when the Bashar al-Assad regime was suspected of carrying out chemical weapon attacks against Syrian opposition groups.
The key concern of a US military withdrawal from Syria is that Turkey will exploit the situation to attack the Kurds, which would be seen as a failure by the coalition to support its ally in the war against Daesh.
Iran opposes Daesh, who they claim carried out a terrorist bombing on a military parade in the southern Iranian city of Ahvaz in September 2018.
Iran retaliated by firing missiles from the country, over Iraq into Southern Syria. The Iranian’s are also seeking to supply the Islamic military organisation Hezbollah in Lebanon with advanced missile systems via Syria.
Iran has a stated aim of overthrowing the Jewish government in Israel.
Israel sees Iran as the main threat to its existence.
Israel has carried out strikes against Iranian forces in Syria as it considers them as a threat on its doorstep and does not want them strengthening Syrian or Hezbollah military capacity.
During raids on the Iranians in Syria, Israel has also launched strikes against Syrian air defence systems.
Israel has occupied the Golan Heights in southwestern Syria since the Six-Day War in 1967.