Hamas is thought to have made improvements in its military capability
Israel's move to ground operations in the Gaza Strip gives Palestinian militants their first chance to trade blows on a more or less equal footing with the Israeli army in the current conflict.
Until now the militants have been impotent to counter Israel's air, sea and ground bombardment - spheres where it enjoys total military superiority.
Hamas and other militant groups have launched dozens of rockets at Israel but - while these are occasionally lethal and cause considerable disruption and sap civilian morale - they are ineffective militarily.
Soldiers of the enemy... you must know that a black destiny is waiting for you
Hamas leader Khaled Meshal
But if the conflict transfers to the narrow alleyways of Jabaliya camp, or any of Gaza's teeming urban areas, it will be a different story.
"Hamas has few tools compared with the Israeli army," says Nicolas Pelham, Senior Analyst with the Middle East Programme of the International Crisis Group.
"But the Israeli operations in built-up urban areas will eliminate some of that huge difference," he added.
Israel possesses formidable tank forces, armoured bulldozers, uncontested use of air power and all the paraphernalia of a modern army, such as night vision and thermal imaging equipment.
But Hamas has had months to prepare for bitter urban warfare which will give its fighters a chance to inflict casualties on the Israeli military.
Hamas is by nature a secretive organisation.
Israeli troops spent 38 years occupying Gaza, but withdrew in 2005
However, analysts believe it has considerably enhanced its military capability since taking control of the Gaza Strip in the summer of 2007.
The takeover handed Hamas the limited arsenal of the routed Palestinian Authority. But more importantly it gave Hamas freedom to operate throughout Gaza without interference from the PA, which was committed to disarming militant groups.
Hamas has had to smuggle all its other weaponry into Gaza - which is under a complete blockade imposed by Israel and supported by Egypt in the south.
This is done via tunnels under the Egypt-Gaza border, which have furnished Hamas with the medium-range rockets that have hit Israeli cities up to 25 miles (40km) away.
Explosives and the ingredients for explosive and rocket propellants are even more easily smuggled into Gaza.
Mortars, anti-tank weapons and some anti-aircraft weapons - not effective against modern jet fighters, but possibly so against older helicopters - are also thought to have come through the Rafah tunnels.
So it was an unsurprisingly bellicose Khaled Meshal, Hamas's Damascus-based leader-in-exile, who spoke in an Arabic TV interview before ground operations began on Saturday night.
"Soldiers of the enemy... you must know that a black destiny is waiting for you, and you will either be killed, injured or imprisoned," he told al-Jazeera television.
Lessons of 2006
The Hamas military wing - the Izz al-Din Qassam Brigades - is thought to have about 15,000 members.
It is therefore vastly outnumbered by Israel's total military capability. But there is no shortage of weapons in Gaza or people who might want to pick up a gun against Israelis forces.
Standards of training and discipline for the Brigades have been raised recently, and it is believed to have fairly sophisticated communications systems.
Palestinian civilian casualties are likely to rise in any ground engagement
The organisation has clearly learnt lessons from the 2006 Lebanon war, when Hezbollah bloodied Israel's nose in a bruising encounter in terrain ideal for guerrilla warfare against a conventional army.
Since then, a number of Hamas members are thought to have spent time with Hezbollah and Iran's Revolutionary Guards movement - leading to improvements in its military training regime and organisational system.
The geography of Gaza may not be as advantageous as south Lebanon, but doubtless many Izz al-Din Qassam Brigades members will be hoping to deal a blow against the Israeli army and be rewarded with what they consider glorious martyrdom in the process.
Israel too, however, appears to have made changes since 2006, analysts say.
Its forces have trained hard for just such an engagement, as well as working on improvements to civil defence, supply lines, planning and public relations.
But the important question now is what does Israel want to achieve from ground operations. The stated Israel aim is to deal a blow to Hamas and prevent or reduce rocket fire.
But if the army does seek to retake urban areas it could play directly into the hands of Hamas - especially the longer its heavy armour remains there. And what happens when Israel pulls out?
"There's no guarantee even if Hamas is removed from power in Gaza that rocket fire will not continue," says Nicolas Pelham of the ICG.
"The fact is that more rockets were being fired from Gaza before the Hamas takeover, not least in the era of chaos, than afterwards."
What seems certain is that Hamas' desire to fight in the heavily populated urban areas, and Israel's apparent willingness to prosecute its war there, could have a devastating effect on Gaza's long-suffering civilian population who have nowhere else to go.