Al-Monitor | Hamidreza Azizi: Six years after the outbreak of civil war in Syria, the eastern part of the country has become a critical hotspot that could determine the balance of power between the various domestic and international forces involved.

While the United States is becoming increasingly assertive in keeping the Syrian army and its allied forces away from the Iraqi border, Syrian President Bashar al-Assad’s main allies, namely Iran and Russia, have started to redefine their strategies to preserve their vital interests in the war-torn country.

The United States' shooting down of a Syrian fighter jet on June 18 was regarded as an indicator of elevated US military activism in Syria in support of its partners. In fact, it was a new peak of direct confrontation between the United States and the Syrian government that had started weeks earlier, when American forces declared it a "red line" if pro-Assad forces were to approach the southeastern al-Tanf region, which hosts a base of the US-led coalition.

Reacting to the shooting down of the Syrian aircraft, Russia drew its own red line, with the Defense Ministry declaring that “any airborne objects found west of the Euphrates River” would be considered targets.

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