CAIRO — The Egyptian militant group Ansar Beit al-Maqdis pledged allegiance to the Islamic State's leader Abu Bakr al-Baghdadi on Monday, joining a growing number of jihadist groups outside of Syria and Iraq who’ve offered their support to the self-declared caliphate.

An audio recording released on the group's Twitter account addressed Egyptians, telling them it is "no use to continue with shameful peace or blasphemous democracy."

They aren't the only ones keen on IS. The disjointed band of IS followers currently includes the city of Derna in Eastern Libya, a Jordanian Salafi group, Pakistani Taliban leaders, a mosque in Denmark and a man in Texas.

But the endorsement by Ansar Beit al-Maqdis draws the IS fight into Egypt, the United States' major ally in the region, and has the power to strengthen both extremist groups. Here's what you need to know about the Islamic State’s newest best friend.

1. They haven’t been around very long

Ansar Beit al-Maqdis (ABM), or “Supporters of Jerusalem,” came into being in Egypt’s Sinai Peninsula in 2011 following the overthrow of longtime autocrat Hosni Mubarak. But it wasn’t until Mubarak’s successor Mohamed Morsi was ousted by the army in July 2013 that they began to target security forces and symbols of the Egyptian state. The US only got around to designating the group a terrorist organization earlier this year.

Estimates for the number of fighters in ABM ranks range from hundreds to a few thousand. They are a combination of Bedouins from the Sinai Desert, non-Bedouin Egyptians, and possibly, some experts say, foreign fighters. Based in Egypt’s Sinai Peninsula, which borders Israel and the Gaza Strip, they have also carried out several attacks in Cairo.

2. They are deadly, and they don’t mind killing civilians

Since July 2013 they have killed hundreds of members of Egypt’s security forces in a series of suicide bombings, drive-by shootings and assassinations. Most of those who have been killed are young security officers, many of them conscripts doing their mandatory military service. One of their biggest attacks came last month, when they killed 31 soldiers in the Sinai, prompting the Egyptian government to adopt ever-tighter security measures.

The group has also targeted civilians. It claimed responsibility for an attack on a tourist bus in Taba in February as it waited to cross into Israel, leaving four people dead. Its fighters also killed an American energy contracter earlier this year.

3. They don’t like Israel

Many of the group’s earlier attacks were directed at Israel. In July of 2012 they blew up a pipeline carrying gas from Egypt to Israel and Jordan. They have launched several rockets at the Southern Israeli town of Eilat and they attacked an Israeli border patrol in September 2012 in response to a film widely perceived to have insulted the Prophet Muhammad.In recent months the group has beheaded and shot several people in the Sinai whom they accuse of providing information to the Israeli and Egyptian militaries.

4. They are well armed

These are not people who simply plant bombs and watch the fallout from their basements. Analysts suggest that ABM has recently managed to recruit more experienced fighters who are able to hold their own when they come under attack. In terms of firepower, the group is known to have portable missile launchers known as Manpads with which they shot down an army helicopter earlier this year.

5. The alliance could help both IS and ABM

IS has many things that make it attractive to an aspiring terrorist franchise — most of all resources, including money, oil and weapons. In addition, the social media-savvy IS has built a strong brand which, coupled with the group’s military successes, has proved a very effective recruiting tool. IS, meanwhile, gains allies across the Red Sea and a deeper pool of potential fighters.