Hamas has up to 20,000 armed men under its command divided between its armed wing, known as the Izzedine Al-Qassam Brigades, and paramilitary police, commonly known as Executive Force.
Unlike al-Qa'ida and its acolytes that work on an ideology of holy war or jihad, the Islam-fuelled militancy of Hamas is more focused on recovering land lost to Israel.
Foot soldiers show little fear of death and the group's ideology conveys great respect on what it calls "shaheed" or martyrs, who die for the cause.
They each carry a Kalashnikov assault rifle and have access to a modest stock of weapons. But their most potent weapon is their stock of rockets with which they attack Israel.
The quality of the troops is questionable. In the early days after the founding of Hamas on December 14, 1987, the Izzedine al-Qassam brigades evolved to fight not just Israel but other rival factions. Members' fighting ability was limited.
But when Hamas was elected to power in January 2006, its leaders moved to create a police force from scratch. In May 2006, the Executive Force was born.
It earned its stripes in June 2007 when it secured Hamas rule over Gaza. A crucial change took place as senior Hamas figures visited Iran for military training. The worry was the Iranian trainers would have transformed Hamas into a potent fighting force.
Israeli troops are currently learning first hand the extent to which this might be true. (© Daily Telegraph, London)