Nearly a decade ago, the U.S. Marines staged mock urban battles designed to test future tactics for fighting in streets and alleys. The war games featured an array of advanced military hardware, including aerial drones with the laser-sharp cameras and micro-robots to scout for mines and potential ambushes.

But the exercises in California and at the Marines' Quantico, Va., base also reinforced the inevitable realities of urban conflict: Troops are drawn into a confusing and difficult arena where hit-and-run guerrillas often have the upper hand and civilians are caught in the crossfire.

"Urban areas can be extraordinary in their level of complexity," said a summary of the 2000-1 maneuvers published by the Rand Corp.

Now, Israel's push into teeming Gaza City has highlighted these risks on a scale and intensity not witnessed since late 2004, when U.S.-led forces launched a grinding, block-by-block showdown against Iraqi insurgents in Fallujah that lasted for nearly three months.

Even as Israel declared Saturday it would halt the attacks opened in late December, the long-term lessons of the incursion are already being weighed by military experts around the world. It's a study in strategies for both sides — standing armed forces and militia groups such as Hamas in Gaza and Hezbollah in Lebanon — as urban centers increasingly become the modern battlefields.

For Hamas, which is chiefly supplied through tunnels under the Egyptian border, the fight is suddenly about holding territory and foiling Israel's advance after years of lobbing rockets from the relative safety of Gaza.

Military strategists are closely watching how Hamas uses its advantages: sniper positions, ability to plant roadside bombs and booby traps and efforts to funnel Israeli forces deeper into narrow streets and crowded neighborhoods where they are more vulnerable to attacks.

"Hamas will seek to suck the (Israeli) forces as much into the urban terrain as possible," said retired British Col. Christopher Langton, a military analyst at the International Institute for Strategic Studies in London. "They will attempt to shape the battlefield."

But this also runs the risk of even more civilian casualties — with more than 1,100 Palestinians already dead in the three-week conflict, about half of them civilians, according to Gaza health officials.

"These are heavy human costs when fighting moves into cities," said Langton. "It's been true through history and it's true today."