After the United States shot down a Syrian military SU-22 over Syria on Sunday, the United States, Russia, and Iran have begun establishing “red lines” for one another, or borders within the nation each respective state’s military assets cannot cross without being engaged as a hostile.

While the establishment of red lines is not a new development in the ongoing conflict with the Islamic State within Syria, the decision to reestablish and reinforce these lines speaks directly to the heightened tensions between external forces and the groups they support within Syria.

Russia issued a warning to the United States after the American F/A-18 Super Hornet shot down the Syrian SU-22 declaring that any U.S. aircraft seen flying west of the Euphrates River would now be seen as hostile, and engaged with Russian anti-aircraft defenses.

Over the weekend, Iran launched a volley of ballistic missiles at ISIS targets within Syria, marking the first such Iranian offensive in decades.  Six missiles with a maximum range of approximately 435 miles were fired from the western region of Iran, flying through Iraqi airspace, before impacting their targets in Deir ez-Zor.