The month of June was bookended by a handful of Molotov cocktails. The results will not benefit the Muslim Brotherhood.

On June 1, an Egyptian national hurled the incendiary bombs at Jewish activists at Boulder, Colorado. On June 30, an 82-year-old victim died of her wounds. The assailant, who had demonstrated allegiance to the Muslim Brotherhood, now faces two counts of first-degree murder.

The attack ignited a bipartisan effort to designate the group as a Foreign Terrorist Organization. Yet lawmakers in both parties seem to forget a critical piece of the Brotherhood puzzle: Qatar.

As it happens, eight years ago this summer, the Gulf Cooperation Council splintered — and the Brotherhood was part of the cause. Saudi Arabia, the United Arab Emirates, and Bahrain, together with Egypt, cut ties with Qatar over its support for extremist groups, particularly the Muslim Brotherhood.

The quartet recalled their ambassadors from Doha and closed their airspace to Qatari planes. Saudi Arabia locked its land border with Qatar, turning the peninsula into a de facto island, and jettisoned Qatari troops from the Saudi-led coalition fighting in Yemen. 

Qatari citizens were given two weeks’ notice to vacate Saudi Arabia, Bahrain, and the UAE. The quartet issued Qatar a list of 13 demands, including that Doha sever ties with the Muslim Brotherhood and other “terrorist groups.”

Four years later, Qatar buried the hatchet with its neighbors due more to American pressure rather than meaningful Qatari reform. And so, everything old has become new again.

Hamas, the Muslim Brotherhood’s Palestinian offshoot, plunged the Middle East into a war that is now 18 months old. In France, a government-commissioned report found that the Muslim Brotherhood is a threat to “the fabric of society and republican institutions.”

Founded in Egypt in 1928, the Muslim Brotherhood has grown over the last century into a decentralized, transnational Islamist movement dedicated to the mission of establishing a global caliphate. 

In the 1950s, Egypt’s nationalist regime cracked down on the Brotherhood, driving members abroad. Qatar welcomed many of them inside its borders, including the group’s de facto spiritual leader, Egyptian cleric Yusuf al-Qaradawi.

While Qatar’s domestic Muslim Brotherhood chapter dissolved in 1999, Doha continued to back the movement abroad. As the Arab Spring swept the Middle East, Qatar backed the Muslim Brotherhood from Egypt to Tunisia to Libya.

In Egypt, Doha poured some $8 billion into Mohammed Morsi’s Muslim Brotherhood government, which rose to power in 2012. Some 13 months later, Morsi’s government collapsed and Qatar offered sanctuary to Egyptian Muslim Brotherhood figures.

Today, the most well-known of Qatar’s Muslim Brotherhood clients is Hamas. Doha began courting Hamas in the 1990s and solidified its relationship with the Palestinian terrorist group after Hamas seized control of Gaza in 2007. 

A former Qatari emir, Sheikh Hamad bin Khalifa al-Thani, pledged $400 million to Gaza when he visited the Strip in 2012 — the first head of state to visit Gaza under Hamas rule.

Qatar went on to shower Hamas-run Gaza with nearly $2 billion, host Hamas’s political headquarters, and provide senior Hamas leaders space to become multi-billionaires. Hamas’s late political chief, Ismail Haniyeh, once described Qatar as Hamas’s “main artery” for fundraising.

In addition, the Qatari-owned news network Al Jazeera puffs up the Brotherhood and exports its ideology to audiences around the world. Al-Qaradawi himself hosted a long-running prime-time talk show on Al Jazeera before his death in 2022. In 2013, Al Jazeera English pulled an anchor off the air because she didn’t show sufficient sympathy.

None of this was lost on the Saudis, Emiratis, Bahrainis, or Egyptians, whose list of demands in 2017 included that Qatar “shut down Al Jazeera and its affiliate stations.”

In this context, American lawmakers have spoken out about the Brotherhood threat. “The Muslim Brotherhood uses political violence to achieve political ends and destabilize American allies,” Senator Cruz said on June 4, arguing that the group warrants designation as an Foreign Terrorist Organization. 

Mr. Cruz led efforts to secure the designation in 2015, 2017, 2020, and 2021. Representative Jared Moskowitz, a Florida Democrat, wrote a letter to President Trump on June 3 urging the administration to “conduct a comprehensive investigation into designating the Muslim Brotherhood” as a terrorist organization.

Exploring options for designating the Muslim Brotherhood is overdue, but without putting Qatar under the microscope, it is insufficient. 

That would mean Congress and the Trump administration re-evaluating Qatar’s Major Non-NATO Ally status, access to American weapons, and joint economic opportunities. 

The administration could also consider replicating elsewhere in the region capabilities housed at Al Udeid Air Base — the largest American military base in the region, situated southwest of Doha.

Mr. Cruz is right that Washington “can no longer afford to avoid the threat” that the Muslim Brotherhood poses “to Americans and American national security.” America must act on the hard truth that Qatar, despite its friendship with the United States, is the wind filling the Brotherhood’s sails.