Since Islamic State (Isis) were formed in their current incarnation in April last year, they have had a dilemma: how to gain legitimacy from the local population while continuing to be ruthless and genocidal against fellow Sunnis.

The decision by the American-led coalition to strike against Isis while overlooking the Assad regime seems to have resolved this dilemma for the jihadist organisation. What Isis will lose in terms of strength and numbers as a result of the air strikes they might gain in terms of legitimacy.

Air strikes against Isis were inevitable, as the group’s advances towards Baghdad, Erbil and northern Syria seemed irreversible by local forces. But the way the US-led coalition, which the UK has now joined, has conducted itself so far threatens to worsen the situation in favour of Isis.

Most importantly, by overlooking the regime of Bashar al-Assad, which caused the death of nearly 200,000 Syrians, the air strikes create the perception that the international coalition is providing a lifeline to the regime. Despite repeated reassurance by Washington, such a perception is likely to become entrenched if the Assad regime begins to fill the vacuum left by the offensive against Isis, especially that there has been no evidence yet that the opposition forces are part of the military strategy against Isis.

The regime might deliberately step up its campaign in some areas to retake areas it has recently lost to the jihadist group to reinforce that perception, as Syrian officials were quick to issue statements that the regime had been briefed about the air raids before they were launched.Many Syrian rebel factions, including ones directly financed by the Americans and the Gulf states, expressed reservations about, or opposition to, the air strikes, including Harakat Hazm, Division 13, Suqour al-Sham.

The significance of such statements is that they are issued by groups currently operating in areas outside Isis control but which are adjacent to Isis front lines. That makes them more capable than other groups of being part of potential ground forces to attack Isis under air cover. Even though some of these groups made such pronouncements mostly for practical reasons, since they are the ones who will bear the consequences of any failure to dislodge Isis as they fight on the ground, they are also concerned that the international campaign will aid the Assad regime.

Regionally, the offensive against Isis has received a similar cynical reaction from groups and people in the Middle East. The Muslim Brotherhood, including prominent figures such as Doha-based Yusuf al-Qaradawi, condemned the attacks inside Syria.

Arab countries that have participated in the international military campaign (Not in soldiers) including Saudi Arabia, the United Arab Emirates and Jordan, have been particularly criticised for failing to push for a formula that undermines Isis and Assad at the same time. In comparison, Iran opposed the air strikes against Isis in Syria while Turkey made it clear that the offensive would fail without moves to undermine the Assad regime, including a no-fly zone. (Turkey is becoming the main culprit in sustaining Al Nusra terrorists in north west Syria)

These attitudes mean that Isis are set to gain from the international campaign against them, if the current strategy does not change. Based on conversations with people from eastern Syria, including Isis members and sympathisers, the offensive against Isis seems to have already achieved one thing for the jihadi group: to push some Isis members who were on the periphery into their core, and neutralise some of their Islamist opponents.

Many of Isis members are new to the group and they are still ideologically uncertain. But since Isis are now face to face with a numerically exaggerated alliance led by Washington, Isis members who could otherwise shift away from the group have become more determined adherents.

Isis can afford to lose their supply lines, infrastructure and many of their members – who are likely to be among the ones who recently joined it – as long as they can compensate by achieving popular recognition. They are already adapting to the campaign, reducing checkpoints (now mostly mobile) to a minimum and relocating weapons warehouses to safe areas in both Iraq and Syria.

People inside Syria say most of the bases or facilities hit by air strikes had been already emptied. While the air raids will surely undermine Isis’s ability to generate revenue by disrupting supply lines from factories or oilfields, Isis can survive without such easy-money resources. Also, it is important to highlight that Isis have established an intricate sleeper cell system that has not been unveiled, even when they felt secure in their territories.

Legitimacy for the fight against Isis cannot be achieved by simply having Sunni countries involved in it, but, rather, by addressing the true reasons that drove tens of thousands of Syrians to rise up against the regime.

Regardless of who is involved in the campaign, the perception is that the allies have overlooked the acts of the Assad regime over the past three years and quickly assembled a major international coalition against a group that the Syrian rebels have been fighting since last summer.

Unless the strategy against Isis shifts to a broader one that appeals to the local communities, the fight against it is doomed.

(Note: the USA still air bomb the Syrian army when it approaches ISIS strongholds)

Hassan Hassan is an analyst with the Delma Institute, a research house in Abu Dhabi. @hxhassan