Since the war between Israel and Hamas broke out in Gaza in October, some have been warning that the localized fighting could erupt into a regional conflict.
Those warnings came when Hezbollah vollied rockets into Israel from across the border in Lebanon and as the U.S. sent two aircraft carriers and supporting ships to the region.
And they came again on Sunday when Iran-backed Houthi rebels in Yemen attacked commercial vessels in the Red Sea in an incident that also involved a U.S. warship on patrol in the area.
U.S. Central Command said the Houthis attacked three ships over several hours using ballistic missiles and drones, several of which American forces shot down.
CENTCOM said it had "every reason to believe that these attacks, while launched by the Houthis in Yemen, are fully enabled by Iran. The United States will consider all appropriate responses in full coordination with its international allies and partners."
Houthi military spokesman Brig. Gen. Yahya Saree took responsibility for attacking two of the ships, saying the group was blocking Israeli ships from passing through the Red Sea until Israel halted its military operations in Gaza.
In addition to the attacks by Hezbollah and the Houthis, other militant groups backed by Iran have carried out dozens of attacks against U.S. military forces spread throughout the Middle East in recent weeks, according to the Pentagon. While these attacks have been frequent, they've so far been on a relatively small scale and the U.S. has responded with limited airstrikes. Yet they point to the volatility in the region and the possibility that attacks could escalate into a much larger battle.
Who are the Houthis, and what do they want?
The Houthis emerged as a rebel group in the late 1980s and '90s, but grew in military might after the turn of the century and went to war with the Yemeni government.
In 2014, the Houthis overthrew the country's government and gained control of the capital, Sanaa, which the militia still controls today. Houthis follow a branch of Shia Islam, as does the Iranian leadership, which helped lead to their alliance.
In 2015, a coalition of countries led by Saudi Arabia launched a military intervention in Yemen on behalf of the internationally recognized government in an attempt to beat back the Houthis. Saudi Arabia is a top rival of Iran, which supports the Houthis with weapons, intelligence and other political and diplomatic aid.
That conflict has been raging for years and spawned the largest humanitarian crisis in the world, according to the United Nations, with more than 24 million people in need of aid and protection.
Still, the Houthis managed to withstand the offensive and remain in control of large swaths of territory and much of the Yemeni population.
Thomas Juneau, a University of Ottawa professor who studies the Middle East, said the Houthis have been emboldened by their ability to resist the Saudi-led attacks, and as a result they've been trying to grow from a domestic power into a regional player in recent years.
"We've seen them attack the [United Arab Emirates, which had allied with Saudi Arabia in the war]. We've seen them attack Saudi Arabia. We have seen them, in the past, attack shipping in the southern half of the Red Sea," he said. "So when the Gaza war started in early October, to me it was a matter of time before the Houthis would become involved militarily."
The attacks likely would also be viewed as messages of support to Iran, Hamas and Hezbollah and may be popular at home too, according to Juneau, where there are strong pro-Palestinian and anti-Israeli attitudes.
"To be seen domestically as not only opposing Israel politically but actually trying to do something about it — i.e. sending missiles and drones — is a classic way to mobilize domestic support by playing on these pro-Palestinian popular feelings," he said.
Will the Red Sea attacks erupt into a broader conflict?
This is not the first time the Houthis have targeted ships — including U.S. naval vessels — in the Red Sea off the country's western coast.
In 2016, missiles were fired from coastal Yemen toward a U.S. Navy destroyer twice in four days. The U.S. responded by firing missiles at three radar installations in Houthi territory.
Juneau said the Houthis didn't target American vessels again for several years, but it's unclear if a similar U.S. response today would have the same deterrent effect.
"It will be much more difficult to do that today than in 2016, because the Houthis are far more powerful now than they were before and they feel much more emboldened," he said.
The Houthis have also fired missiles directly at Israel before, but in one such attack last month Israel's military stopped it with its air defenses.
Going after commercial ships also gives the Houthis leverage, Juneau added, to negotiate with impacted nations and raise the ambitious militia group's international profile.
Last month, Japan announced it was approaching the group for talks after a Japanese-operated cargo ship was hijacked in the Red Sea.
"That's exactly what the Houthis want," Juneau said. "By forcing the Japanese government — which is a very important G7 country and so on — to deal with them directly, they are looking for recognition, at least de facto, of their status as the governing authority inside Yemen."
STEVE INSKEEP, HOST:
We begin with the low-level expansion of the war between Israel and Hamas. Allies of Hamas have used rockets and drones in several parts of the region in recent weeks and that includes the waters of the Red Sea. In an incident last weekend, an armed group that controls much of nearby Yemen fired on passing commercial ships. The U.S. Navy, which protects them, has fired back. Now, Yemen's Houthi rebels count themselves as allies of Hamas and enemies of Israel, but is there more to their involvement? NPR's Joe Hernandez is following the story.
JOE HERNANDEZ, BYLINE: The Houthis say they're attacking ships with links to Israel, but one expert I spoke to about this also says the Houthis feel emboldened right now to carry out these kinds of attacks. The group overthrew Yemen's government in 2014, and in the years since then has managed to withstand this outside military intervention led by Saudi Arabia, which, of course, is a rival to Iran. So the Houthis now feel like they're in a position to grow from a domestic power to a regional one. Thomas Juneau is a professor at the University of Ottawa. He studies the Middle East, and here's how he put it to me.
THOMAS JUNEAU: When the Gaza war started in early October, to me, it was a matter of time before the Houthis would become involved militarily.
HERNANDEZ: Juneau says there are a couple other reasons for these attacks from the Houthis. One is they send a message of support to Iran, Hamas and Hezbollah, and the other is that it helps them gain favor at home in Yemen where he says there's wide support for the Palestinian cause and opposition to Israel.
INSKEEP: OK. So what happened in this most recent incident?
HERNANDEZ: Well, the U.S. Central Command reported that the Houthis attacked three vessels over several hours on Sunday, apparently using both ballistic missiles and drones. The naval destroyer, the USS Carney, was on patrol in the area at the time and responded to several of the attacks, in some cases shooting down several Houthi drones. In a statement, CentCom said the attacks were, quote, "fully enabled by Iran" and that the U.S. would consider, quote, "all appropriate responses and full coordination with its international allies and partners." And a Houthi military spokesman did take credit for attacking two of the ships, according to the Associated Press.
INSKEEP: OK. You said all appropriate responses. Other than shooting down incoming projectiles, what can the United States do about this?
HERNANDEZ: Well, it's unclear. It's not the first time the Houthis have targeted ships in the Red Sea, nor is it the first time they've targeted U.S. naval vessels. In 2016, missiles were fired from coastal Yemen toward a U.S. Navy destroyer twice in four days, and the U.S. responded at that time by firing missiles of its own at three radar installations in Houthi territory. And that stopped the Houthis from targeting American ships for several years. But Thomas Juneau says it's unclear if a similar U.S. response today would have the same effect.
JUNEAU: Can the U.S. reestablish a form of mutual deterrence in the Red Sea with the Houthis? It will be much more difficult to do that today than in 2016, because the Houthis are far more powerful now than they were before, and they feel much more emboldened.
HERNANDEZ: So what he says does seem clear is that the U.S. and Iran don't want any direct escalations with each other. And I should add that other Iran-backed militant groups have carried out some attacks on U.S. forces, but they've mostly been on a smaller scale, and the U.S. has responded with limited airstrikes.
INSKEEP: NPR's Joe Hernandez, thanks so much.
HERNANDEZ: You're welcome. Transcript provided by NPR, Copyright NPR.