The already crowded skies above Syria turned even more chaotic on Sunday as the United States shot down a Syrian aircraft for the first time and Iran launched medium-range missiles from within its own territory towards targets in Syria.

Only a few weeks ago, it seemed as if the Syrian Civil War was starting to wind down. Now, however, it appears another escalation could be imminent.

The six Zolfiqar missiles fired by Iran at Isis targets were in retaliation to the Daesh attacks two weeks ago on the Iranian parliament and the Ayatollah Khomeini mausoleum, but they were also a statement of intent.

Iran has not launched missiles against another country since the Iran-Iraq War of the 1980s. Sunday’s missile strikes were not just an act of vengeance for the Tehran attacks, they were also a clear message that the Iranians now consider Syria their backyard.

Despite the claims by Iranian regime media that the missiles caused widespread damage, Israeli intelligence sources maintain that only one of the six missiles hit their target. But actual damage is not the main signal. The missiles overflew Iraq, another section of the “Shi’a Crescent”, a corridor reaching all the way to the Mediterranean that Iran is trying to create. The missile launch underlines the lengths they are prepared to go to in achieving their strategic grand design.

Meanwhile, the shooting down of a Syrian Sukhoi Su-22 by a US Navy F-18E Super Hornet could have much wider implications.

When the Trump administration launched its Tomahawk missile attack on Syria’s Shayrat airbase, in retaliation to the Assad regime’s use of chemical weapons against civilians, there was a widespread view that it was a one-off strike. However, in recent weeks US aircraft have carried out at least three strikes on forces loyal to the Assad-Iran-Russia alliance which were threatening US-backed groups on the ground.

Sunday’s one-sided dog-fight came after the Syrian aircraft was bombing, according to the US military, a unit of the Syrian Democratic Forces, the mainly Kurdish militia which the Trump administration is backing to capture Daesh’s headquarters in Raqqah. The regime claimed that their aircraft was bombing Daesh.

The Americans have yet to declare a clear strategy in Syria. So far, it looks mainly like a do-the-opposite-of-Obama policy. The previous administration also supported some of the Syrian rebel groups with arms and money, but did not intervene on their behalf when they came under Syrian or Iranian attack.

The red line Trump has yet to cross in Syria is direct confrontation with Russia, which is much more heavily invested in Syria than the US. Moscow has responded to the downing of the Syrian jet with aggressive statements about regarding any foreign aircraft west of the Euphrates River as “hostile targets” from now on.

In essence, this could mean the first direct clash between Russian and American pilots in the air since the Vietnam War. Whether the mercurial Mr Trump, already under investigation for his questionable ties to Russia, will call the Kremlin’s bluff, is impossible to foresee.