The group's choice of targets is a clear sign of its intention to inflame Sunni/Alawite tensions, raise the price of Moscow's intervention, and assert its symbolic leadership over the rebellion.

On May 23, the Islamic State (IS) perpetrated suicide bombings in Tartus and Jableh, killing 154 people and wounding more than 300. This was the first time either coastal city had been targeted by such attacks since the beginning of the war. Tartus in particular had seemed like a haven up until Monday. It was still an attractive tourist destination because of its wide beaches, and it was in the middle of a construction boom given the arrival of internally displaced people (IDPs) from other parts of Syria -- not just the Assad regime's fellow Alawites from Damascus, but also members of the Sunni majority from all across the country. Many Syrian refugees had even returned from Lebanon to Tartus because they considered life to be cheaper and safer there.

IS operatives can conduct simultaneous attacks of this nature rather easily given the corruption and nonchalance at coastal security checkpoints. I saw this problem firsthand when I visited Tartus and Latakia last month. After I crossed the border from Beirut via taxi, nobody asked me for my passport or searched my suitcase. The driver was known at each checkpoint, and by giving 100-200 Syrian pounds (10-20 cents) to those who stopped us, he was able to quietly proceed without hassle. Thanks to rampant corruption, he had also obtained a special permit to use military roads, further enabling him to avoid stringent controls. So it would be quite simple for terrorists to regularly infiltrate the Alawite heartland, which is also home to Russia's main bases in Syria. Moreover, IS could readily establish sleeper cell among its fellow Sunnis in these areas, who number in the hundreds of thousands (both locals and IDPs).

Through the latest attacks, the Islamic State is attempting to send different messages. The first is for the Alawites -- IS wants to show them that the Assad regime cannot protect them. After all, the group has not attacked the nearby coastal cities of Banias and Latakia, which have larger Sunni populations. In Latakia's case, IDP flows have made Sunnis the majority, and IS likely prefers to avoid the risk of heavy Sunni casualties there. Regime security efforts are also more serious in Banias and Latakia, where Sunni neighborhoods erupted into armed rebellion in 2011-2012, which was not the case in Jableh and Tartus.

Sending such violent signals to the Alawites could have multiple ripple effects. IS leaders likely hope that Alawite soldiers serving in hotspots on the eastern front (e.g., Deir al-Zour, Palmyra) will refuse to fight if their families back in Tartus and other cities are not given better protection; the regime might even decide to redeploy eastern troops to the coast. The group also aims to spark discontent against the regime and Alawite reprisals against Sunnis. On February 21, IS attacks in Homs affected Alawite neighborhoods and provoked strong discontent against local authorities and the security apparatus, with people denouncing the corruption and inefficiency of officers. For now, such antipathy does not extend to Bashar al-Assad himself, but that could change if attacks continue. Meanwhile, Alawite reprisals against Sunnis could undermine the regime and its army, since many Sunnis are still fighting on Assad's side. On Monday, Alawites attacked al-Karnak camp in Tartus, home to 400 Sunni families from Aleppo and Idlib; according to unofficial sources, seven Sunnis were killed.

Yet the Islamic State's most important message is presumably to Moscow. Russia's only naval base in Syria is located in Tartus, while Jableh is close to Hmeimim, Russia's main air base. Moscow is also attempting to rehabilitate the old Soviet submarine base in Jableh. IS has already shown a pattern of targeting Russian infrastructure, most recently Tiyas airfield between Homs and Palmyra, according to the BBC. IS leaders are well aware that Moscow's assistance enabled the Syrian army to retake Palmyra and set its sights on Deir al-Zour, so they aim to increase the price of the Russian intervention and force a withdrawal from the Syrian theater, or at least from the eastern fronts.

Finally, Monday's bombings send a message to other rebel groups. Although the Islamic State's goals and methods often differ from those of Syria's various anti-Assad factions, it still wants to be regarded as the leader of the fight against the regime, Russia, and the Alawite community. It will therefore continue trying to show that it is more effective and more ruthless than al-Qaeda affiliate Jabhat al-Nusra, currently its main rival for that title.

Fabrice Balanche, an associate professor and research director at the University of Lyon 2, is a visiting fellow at The Washington Institute.