Worries about another war in the Middle East receded modestly when President Donald Trump rejected the wishes of his hawkish advisers and called off a planned airstrike on Iran for shooting down a U.S. spy drone. However, his decision to impose new economic sanctions on the Iranian regime has worsened already alarming tensions, and an armed conflict remains a serious possibility. Iran also now has a stronger incentive to cause maximum problems for the United States and its key ally, Saudi Arabia.
The toxic U.S.-Iranian relationship is just one component of a matrix of intense geo-strategic rivalries in the region. An especially dangerous aspect is the Sunni-Shia religious and political feud, which pits Iran, the leading Shia power, against Saudi Arabia, a key Sunni power. That rivalry for regional preeminence is already playing out in several arenas. It is a major element in the Syrian civil war, the bloodbath in Yemen, and the jockeying for political influence in Iraq. 
Bahrain may be the next country in which Tehran and Riyadh engage in a brass knuckle fight for dominance. The hostile, deteriorating relationship between the United States and Iran significantly increases the likelihood of an Iranian initiative. Indeed, Bahrain is an ideal location for Tehran to give both Washington and Riyadh bloody noses.
Bahrain’s religious composition creates an inherent powder keg. Barely 20 percent of the country’s citizens are Sunni, while over 50 percent are Shia. Yet the government is a brutal autocracy under the total control of a Sunni royal family. There was a major Shia uprising in 2011, and tensions flared again with large anti-government demonstrations in May 2017. 
Saudi Arabia intervened with several thousands of its own troops in 2011 to keep its Sunni client regime in power, and Riyadh has maintained a substantial, if relatively concealed, security presence in the country since then. The Bahrain government has imprisoned numerous Shia political activists, and only recently did the king restore citizenship to more than 500 individuals whom the rubber-stamp courts had stripped of that status. Human Rights Watch, Amnesty International, and other organizations have repeatedly issued reports condemning the regime in Manama for human rights violations, including jailing critics and torturing them.  
U.S. policy toward Bahrain reflects brazen hypocrisy. Even as Obama administration officials routinely condemned Iran for interference in the internal affairs of Iraq, Syria, and Lebanon, Washington’s criticism of the 2011 Saudi intervention in Bahrain was utterly tepid and pro-forma. Subsequent comments by both the Obama and Trump administrations have been no less hypocritical. Indeed, officials routinely stress the importance and enduring quality of the U.S. ties to both Bahrain and Saudi Arabia.
That stance, while cynical and morally offensive, is not surprising. Not only does Washington favor Riyadh in its rivalry with Tehran, the United States regards Saudi Arabia as an extremely valuable ally overall and habitually excuses the regime’s abominable human-rights record. The Trump administration has even brushed offstrong evidence that Crown Prince Mohammed bin Salman ordered the assassination and dismemberment of Washington Post journalist (and U.S. citizen) Jamal Khashoggi. Instead, Trump emphasizes the Kingdom’s economic importance to the United States—especially as a large-scale buyer of U.S. weapons. The administration also continues to provide active assistance to Riyadh in the form of intelligence information (and, until recently, by refueling combat aircraft) to the Saudi-led, atrocity-ridden war in Yemen.
Given that track record, Washington is not about to undercut Riyadh’s position with its Bahraini client. U.S. leaders also have an ample incentive of their own to want the Sunni autocracy to remain in power in Manama. The U.S. fifth fleet is based in Bahrain. Although if absolutely necessary, Washington likely could find another home port for that force, such a change would take time and might well be in a less central location. U.S. political and military leaders have no desire to take the chance, so they continue to look the other way as Riyadh and Manama trample the political rights and even the fundamental civil rights of Bahrain’s Shia majority. Washington insists that Bahrain plays “a key role in the region’s security architecture” and is a “vital” U.S. partner. U.S. leaders seem intent on continuing to arm the Manama regime, despite its human rights abuses.
Members of that majority, though, would be very useful allies or proxies in a campaign to cause headaches for the United States and Saudi Arabia. It certainly would be consistent with Iran’s overall regional strategy. Tehran has expended considerable (and apparently successful) effort to help keep Syria’s Bashar al-Assad from being ousted. The Iranian government also has strong ties to its Hezbollah allies in Lebanon and pro-Iranian Shia militias in Iraq. And Tehran has backed Houthi forces in Yemen—although not to the extent that Western propaganda about Iranian “interference” would suggest.
Iran has at least as great an incentive to back the disgruntled Shia majority in Bahrain as it does friendly forces in those other countries. Indeed, the religious incentive may be even greater. Both Assad’s Alawites and the Houthis in Yemen are Shia offshoots with major doctrinal deviations; the Bahrain community’s practice is closer to the Shia faith adhered to in Iran.
Trump administration officials and much of the U.S. foreign policy community have been too complacent about the likelihood of serious trouble in Bahrain. They seem to believe that there is little danger that a repetition of the 2017 turbulence, much less the even more widespread disorders in 2011, will recur. The situation indeed has been reasonably quiet since the suppression of the 2017 demonstrations, but complacency is unwarranted and potentially dangerous. Even now, the apparent calm is deceptive; a low-level insurgency continues to smolder. 
Members of Bahrain’s oppressed Shia majority constitute a potential powder keg waiting to explode. By tightening the already severe economic screws on Iran and continuing to back Riyadh’s quest for regional preeminence, the United States has given Iranian leaders a huge incentive to light the fuse. 

Ted Galen Carpenter, a senior fellow in security studies at the Cato Institute and a contributing editor at The American Conservative, is the author of 12 books and more than 800 articles on international affairs. His latest book is Gullible Superpower: U.S. Support for Bogus Foreign Democratic Movements (2019).