(NewsNation) — Ships in the Red Sea have come under attack by the Houthi rebels in Yemen in recent weeks.

Several of these attacks have damaged vessels. As a result, multiple shipping companies ordered their ships to hold in place and not enter the Bab el-Mandeb Strait, which connects the Red Sea to the Gulf of Aden, until the security situation can be addressed.

On Monday, the U.S. military’s Central Command reported two more attacks on commercial vessels in the Southern Red Sea.

Who are the Houthi rebels?

The Houthis have their roots in a movement that started during the 1990s in northern Yemen. This movement was started to protect and revive the Zaydi sect of Shi’ite Islam, who had once ruled Yemen. Zaydism, according to the Middle East Institute, had been the religion that ruled Yemen for a thousand years, but was severely repressed after a civil war in the 1960s.

Hussein Badreddin al-Houthi led the Zaydi movement, and shifted it toward political activism, the Council of Foreign Relations said.

In 2003, American troops invaded Iraq, which deeply radicalized the Houthi movement, the Brookings Institute writes. Yemeni President Ali Abdullah Saleh was seen as supportive of the United States, but al-Houthi opposed the invasion. After police moved to arrest al-Houthi in 2004, the first of six rounds of armed conflict between his followers and the Yemeni state began. Friction with the government grew, leading to a series of guerrilla wars between the Houthis and Yemen’s national army.

The Houthis seized Sanaa, the capital of Yemen, in 2014 and their power grew. Saudi Arabia, worried by the growing influence of Iran along its border, intervened in 2015 in support of the Yemeni government. Iran, meanwhile, was behind the Houthis. Houthis ended up establishing control over much of the north and other big population centers, Reuters writes.

The two groups continued warring until a ceasefire between the Houthi rebels and Yemeni government in 2022.

What kind of support do they have?

Iran has given its support to the Houthis, as they both have the same enemy — Saudi Arabia, the Brookings Institute said. A Saudi-led coalition made of nine Arab countries has long accused Iran of arming, training and funding the rebel group, but the Houthis denied this, saying they develop their own weapons.

The United States believes Iran’s Islamic Revolutionary Guard Corps is helping the Houthis plan and carry out their missile and drone attacks in the Red Sea. Iran, though, has said they are not.

The Houthis are, however, part of the Axis of Resistance, a group of different anti-Western forces across the Middle East. NPR writes those in the Axis of Resistance get varying degrees of support from Iran.

Why are they attacking ships in the Red Sea?

On Oct. 31, the Houthis announced they fired drones and missiles at Israel, saying they would not stop the attacks until “Israeli aggression stops.”

Then, in December, the Houthis took this a step further, saying they’d target all ships going to Israel and warning all international shipping companies against dealing with Israeli ports.

A Dec.9 statement said all ships will continue to be targeted by the Houthis if Gaza does not receive the food and medicine they need.

The point of this, the Houthis claimed, is to support the Palestinian people “until Israel’s aggression ends.”

At a Monday briefing, Defense Secretary Lloyd Austin said the Houthis have “violated international law” by harassing ships in the Red Sea.

“So we’re taking action to build an international coalition to address this threat,” Austin said to NewsNation partner The Hill. “This is not just a U.S. issue — this is an international problem, and it deserves an international response.”

What has the United States response been?

The United States announced Tuesday it and a host of other nations created a new force to protect ships transiting the Red Sea.

The United Kingdom, Bahrain, Canada, France, Italy, Netherlands, Norway, Seychelles and Spain have joined the new maritime security mission, Austin said.

Called Operation Prosperity Guardian, military ships will be positioned to provide umbrella protection to as many vessels as they can at a given time, an official told The Associated Press.

The Hill reports Operation Prosperity Guardian will be managed by Task Force 153, a component of the Combined Maritime Forces that defends the Red Sea and the Bab el-Mandeb Strait.

In addition to the task force, Austin also said he would convene a meeting with foreign leaders to talk about how to make the Red Sea free from attacks.

The Associated Press and Reuters contributed to this story.