However, Andrew Exum, a former US army officer who has studied Israel's military campaigns, said the IDF had a long history of mistakes causing many civilian casualties.
"Errant artillery and air strikes have unfortunately been something of a theme in Israel's conflicts in both southern Lebanon and Gaza over the past two decades. There are good strategic reasons to avoid using air power and artillery in these conflicts: they tend to be pretty indiscriminate in their effects and make it difficult for the population under fire to figure out what they're supposed to do to be safe," said Exum, who was a defence department special adviser on the Middle East.
"I'm not sure what the issue is. In 2006 and 2008, it was pretty clear the IDF's combined armed skills – their ability to integrate artillery and air power into ground campaigns – had atrophied since the withdrawal from Lebanon in 2000. But I don't know whether the issue remains poor training, a lack of forward observers talking to the artillery batteries and aircraft, or commanders who just don't think avoiding civilian casualties is a priority."
However, military analysts and human rights observers say the IDF is still using unguided, indirect fire with high-explosive shells, which they argue is inappropriate for a densely populated area like Gaza – where 1.8 million people live in an area the size of the Isle of Wight. The biggest artillery weapon being used is a 155mm howitzer, mounted on tracks to make it mobile. It typically fires a fragmentation shell weighing 44kg that spreads shrapnel over a wide area. Such shells have a lethal radius of 50 to 150 metres and causes injury up to 300 metres from its point of impact. Furthermore, such indirect-fire artillery (meaning it is fired out of direct sight of the target) has a margin of error of 200 to 300 metres.
The use of indirect artillery fire in residential areas is not forbidden under international humanitarian law, but its legality depends on a balance between potential military gain against risk of harm to non-combatants. On that basis, Donatella Rovera, Amnesty International's senior crisis response adviser, said it was hard to see a military justification for its use in Gaza. "The margin of error of an artillery shell is well known. If you are shooting into a civilian area, there is a high chance of hitting civilians and a low chance of hitting your military objective, unless your military objective is to terrorise and punish a population," she said.
The IDF is reported to have a "safety zone", the closest an artillery target can be to civilians areas, of 100 metres. That is significantly less than the casualty radius of 155mm artillery shells, and Human Rights Watch found in a 2007 report that the rule appeared to be ignored in Gaza.
