Members of Houthi security forces stand guard at a rally in Sanaa, Yemen, on July 17. Khaled Abdullah/Reuters

Pakistan’s foreign minister has said three of its nationals were killed in an attack by the Iran-backed Huthi militia on a commercial vessel in the Red Sea.

This marks the first fatalities in the Red Sea since the Yemen-based militant group declared a blockade of the Bab al-Mandeb Strait on July 20.

Here’s a closer look at the Huthis and how they got to where they are:

The Huthi movement, also known as Ansar Allah (Supporters of God), is one side of the Yemeni civil war. It emerged in the 1990s, when its leader, Hussein al-Huthi, launched “Believing Youth,” a religious revival movement for a centuries-old subsect of Shia Islam called Zaidism.

The Zaidis ruled Yemen for centuries but were marginalized under the Sunni regime that came to power after the 1962 civil war. Al-Huthi’s movement was founded to represent Zaidis and resist radical Sunnism, particularly Wahhabi ideas from Saudi Arabia. His closest followers became known as Huthis.

Yemen’s civil war began in 2014, when Huthi forces stormed the capital Sanaa and toppled the internationally recognized and Saudi-backed government. The conflict spiraled into a wider war in 2015 when a Saudi-led coalition intervened in an attempt to beat back the Huthis.

Nowadays, Sanaa is still under Huthi control, alongside much of the west of the country.

The Huthis are backed by Iran, which began increasing its aid to the group in 2014 as the civil war escalated and as its rivalry with Saudi Arabia intensified. Iran has provided the group with weapons and technology for, among other things, sea mines, ballistic and cruise missiles, and unmanned aerial vehicles, according to a 2021 report from the Center for Strategic and International Studies.

The Huthis form part of Iran’s so-called “Axis of Resistance” – an anti-Israel and anti-Western alliance of regional militias backed by the Islamic Republic.

CNN’s Sophia Saifi and Rhea Mogul contributed to this reporting.