Attacks on empty buildings didn't work.. Ceasefire offers didn't work. Limited strikes over a period of weeks didn't work. The IDF announcing on the very eve of the campaign that they would have to invade Gaza didn't work. Hamas responded by boasting that they would outlast the infidels. Then they expanded their rocket fire to hit the 100,000 person city of Ashkelon and rained down almost 100 rockets in 2 days:

Hamas, for its part, has adopted an extreme, uncompromising stance. Conversations with its leaders sometimes give rise to the suspicion that they are out of touch with the military reality on the ground, in which their forces are suffering more and more casualties. One Hamas operative went so far as to refer to the prophet Mohammed in order to stress Gaza residents? ability to withstand the pressure. "The Prophet Mohammed managed to survive for three years under siege by the infidels, while eating moldy food, or none at all," he pointed out.

They've been preparing for this war for over a year and a half:

The Hamas organization in the Gaza Strip has assembled an armed and trained force of about 7,500 fighters... When Israel goes in and has to destroy this thing - which is essentially a professional army hiding in civilian areas, enjoying all of the benefits and meetings none of the obligations of legal warfare - the din of "atrocity" and "massacre" from the international community will be deafening. And forgotten in everything will be the very basic, apparently-too-unsophisticated fact that the Palestinian people elected these people to represent them and armed them to fight a war. Because Israel will eventually have to go in and destroy this army - the Palestinians aren't going to settle for launching rockets at Israeli civilians every few days forever, ya know.

By last October they already had a sophisticated Hezbollah-like bunker system designed to wage a drawn out conflict. The IDF recently discovered Hezbollah-style underground silos in Gaza - the better to launch rockets and missiles via remote control. And so Barak finally did what any other country would have done literally years ago:

Operation "Warm Winter" has finished its first stage – targeting terror infrastructure in the Gaza Strip neighborhoods of Sajaiya and Jabalya, the IDF said Saturday. The operation's first stage also targeted ditches and similar places used as firing grounds by launchers, which were blown up. The second stage of the operation includes patrolling urban areas on a search-and-destroy mission – a hunt for hidden weapons. "The military operation against all ranks responsible for Qassams will continue. The gloves are off and we have no intention of sitting on the sidelines while rockets are being fired," said a security source. The massive strikes, he added, will continue and may even increase... The IDF denied the Palestinians' claims of mass casualties among innocent residents, citing only a few such incidents were known. Hamas, said the IDF, often states false casualty claims in order to generate sympathy in the international community... The IDF's main concern continues to be Warm Winter's final price tag: Hamas has fortified its strongholds and has snipers war-ready. "Overall, our forces are doing admirable work," said the officers present at the briefing.

Hamas has repeatedly and enthusiastically been trying to lure the IDF back into the Gaza Strip. They've got bunkers in civilian areas and use apartment buildings as military bases. And despite these Palestinian war crimes, the IDF has gone out of its way to avoid civilian casualties. All of that will of course be ignored in the enthusiastic round of anti-Israel demonization that is set to begin right. about. now.

References:
* IDF bombs Gaza buildings used for launching rockets at Israel [Ha'aretz]
* Hamas Responds To Ceasefire Proposal By Lobbing Missiles On Sderot Schoolchildren [MR]
* IDF kills 5 gunmen in Gaza, Nablus [YNet]
* Gaza raid likely as attacks intensify [The Australian]
* ANALYSIS / Uncompromising Hamas is in trouble [Ha'aretz]
* The Hamas organization in the Gaza Strip has assembled an armed and trained force of about 7,500 fighters. [MR]
* Hamas Has Smuggled 112 Tons Of Explosives Into Gaza, Preparing Bunker System For All Out War (Plus: Israel Suspends Decision To Cut Fuel On Humanitarian Grounds) [MR]
* IDF finds Kassam silos in Gaza [JPost]
* IDF gears up for Gaza op [YNet]
* Arabs to UN: Scold Israel for hitting Gaza back! [Hot Air]

Previously:
* Hamas Smuggles Katyushas Into Gaza, Fires Them At Israeli Schools And Hospitals (Plus: Eight Mortars Fired At Israeli Civilians, One Scores Direct Hit)
* Hamas Fires Five More Rockets At Israeli Schools And Hospitals, Shoots Up Israelis In The West Bank, Then Cries Pathetically About Limited Israeli Retaliation (Plus: Olmert: Of Course We Won't Punish Gaza)
* Hamas Has 200 Tons Of Explosives That The US Gave To Fatah (Plus: Egypt Says It's Israel's Fault)