Hamas, an Arab acronym for Islamic Resistance Movement, was founded in 1987 after an eruption of protests and riots over Israel's military occupation of the West Bank and Gaza.
Its founder Sheik Ahmed Yassin was a quadriplegic who was nearly blind, and had been reliant on a wheelchair due to a sporting accident at the age of 12. Hamas maintains that it is a chapter of the Muslim Brotherhood – a transnational Sunni Islamist organization founded in Egypt by Islamic scholar and schoolteacher Hassan al-Banna in 1928.
Yassin formulated the Hamas Charter which envisioned an Islamic State comprising Israel, West Bank and Gaza.
Hamas subsequently signaled it was willing to accept a two-state solution based on Israel's borders as they were before 1967, but it rejects Israel's right to exist and opposes the Oslo Accords negotiated by Israel and the Palestine Liberation Organization in the 1990s.
Where is Hamas' headquarters?
Hamas largely operates in Gaza City, but also has operations in the West Bank, alongside an overseas presence.
In the comforts of Doha, Qatar, a safe distance away from the current war, lies one of Hamas' offices.
Only yesterday, a video of Ismail Haniyeh, the Hamas leader, was seen in an air-conditioned room in a top hotel in Doha, accompanied by 12 others.
He later met Iran's Foreign Minister Hossein Amirabdollahian in the city.
Hamas also had an office in Syria's Damascus', before closing it in 2012.
Last year, it announced that it would reopen its offices in Damascus again.
Who funds Hamas?
Iran is said to be a big financial supporter of Hamas.
In 2019, the US Treasury said the fighters' military wing, known as the Al-Qassam Brigades, had received more than $200 million from Iran's Islamic Revolutionary Guard Corps in the previous four years.
It has also allegedly supplied weapons to the group.
But Tehran isn't the only channel.
The Al-Qassam Brigades is said to have received cryptocurrency donations, particularly after the 2021 conflict.
Wallets connected to Hamas received about $41 million over a similar time period, according to research by crypto analytics and software firm, Tel Aviv-based BitOK.
Oftentimes, Israeli banks are used for the transactions.
In October this year, Israeli police said they froze a Barclays bank account the authorities said was linked to Hamas fundraising and blocked cryptocurrency accounts used to gather donations, without specifying how many accounts or the value of the assets.
Some countries have also provided relief aid and other funding for civilian purposes.
Qatar has provided hundreds of millions of dollars in aid to both Hamas and the Palestinian Authority in the West Bank to fund reconstruction and government expenses after Israeli bombardments.