But their plan is not without serious risks, analysts warn.
Bahrain, Qatar, Saudi Arabia and the United Arab Emirates could end up strengthening President Bashar al-Assad and face anger at home over their bombings of fellow Sunni Muslims.
"I expect this is going to be causing a great deal of concern that the Gulf is inadvertently serving as Assad's air force," said Frederic Wehrey, a Middle East expert at the Carnegie Endowment for International Peace.
"In addition, the Gulf states could face domestic criticism and agitation over their participation in a US-led coalition," he said.
The four Gulf monarchies, along with Jordan, joined the US-led campaign on Tuesday that launched air strikes on IS positions inside Syria for the first time.
The exact nature of their involvement has been vague and it is not clear exactly which strikes their planes have carried out.
But even if Washington is behind the vast majority of attacks, the symbolic importance of having Sunni-ruled Arab states on side against the Sunni extremists of IS has been crucial.
Experts said the Gulf governments were well aware of this and insisted before signing on to the air campaign, which started last month in Iraq, that it be expanded to Syria as well.
"The GCC (Gulf Cooperation Council) condition was very clear: no support of US policy to deal with ISIS in Iraq without military action in Syria," said Mustafa Alani from the Geneva-based Gulf Research Centre, using an alternative name for the jihadist group.
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Their first objective, said expert Abdulkhaleq Abdulla, is to counter IS, which some governments in the region were accused of initially helping and financing.
- Danger of 'radical voices' -
"ISIS is in fact in many ways a threat to their security and also to the ideological legitimacy of Saudi Arabia" as a religious centre, said Abdulla, a professor of political science at Emirates University.
Their second objective, experts said, is in the long run to undermine Assad, whose minority Alawite, Tehran-backed regime they despise.
Alani said the US-led coalition was essentially creating a "no-fly" zone in parts of Syria, undermining Damascus's control over its territory and its capacity to defend itself.
"The ultimate goal is to bring Assad to a new round of (peace) talks... with the hope that the end result will be the removal of Assad," Abdulla said. "That is the strategy."
But experts warned it could backfire by easing the pressure on Assad from IS, the most effective group battling his regime.
And in particular for Saudi Arabia, which has also agreed to train Syrian rebels on its territory, the campaign could stir widespread outrage at home.
"The US bombing of ISIS is unpopular with a range of Saudis," Wehrey said. "There is the perception in the Gulf that the US is attacking Sunni power while privileging minorities, especially Shia.
"Radical voices in the Gulf could capitalise on this sentiment."