Israeli warplanes struck the Palestinian Interior Ministry building in Gaza on Dec. 29 as the Israeli assault entered its third day amid continued rocket fire on Israel from Gaza. Though Israel has no interest in reoccupying the Gaza Strip, as Israeli Foreign Minister Tzipi Livni has reiterated, Israeli ground incursions certainly are possible. Israel Defense Forces (IDF) spokesman Brig. Gen. Avi Benayahu has argued the case for a sustained operation that probably will continue into the new year. The implications of the Israeli action for Hamas are significant. The current outbreak of hostilities was not a surprise for either side. A 6-month-old Israeli-Hamas cease-fire expired Dec. 19. And Hamas and the more militant organizations in Gaza, like Palestinian Islamic Jihad and other jihadist groups, have been digging in since Israel unilaterally withdrew from the territory in 2005, despite the occasional Israeli raid. Since then, the IDF has kept a close eye on Gaza and has continually updated its contingency plans. Being an occupying power in Gaza was more trouble than it was worth for the IDF, which is an inherently small military force to begin with due to Israeli demographics. Freeing itself from that entanglement increased the IDF's ability to deal with security challenges from Syria to Hezbollah. But it has been clear to Israel for some time that additional military action might be required in Gaza. Israel already has called up some 6,500 reservists, moved reinforcements to the border and put military forces there on alert. At the very least, the IDF is positioning itself to carry out ground raids — and might already be preparing to execute them. Meanwhile, Israeli airstrikes on identified targets in the Gaza Strip are ongoing, with targets including tunnel complexes, militant operatives and weapons caches. The military objective for Israel is to eviscerate Hamas' capability to strike at Israeli territory. Rocket strikes already have seen ranges indicative of Grad artillery rockets, a significant escalation from the homemade Qassams that have long characterized Gaza militancy. This objective could very well require some sort of Israeli ground incursions. And there is little to stop the IDF from taking whatever military action it deems necessary. Qassams are manufactured in garages in Gaza out of crude materials relatively easy to obtain in the territory. About a year ago, indications emerged that the Qassam's design — specifically the fuel mixture — had been tweaked to extend the rockets' shelf life beyond a matter of days. The IDF immediately identified this as a concern because the rockets now could be more readily dispersed and stored for use in a crisis. Only a few months earlier, in October 2007, signs emerged that Grad artillery rockets manufactured outside Gaza and built to still crude — but nevertheless more exacting — military standards than the Qassams had been delivered to Gaza. These indications have been reinforced in the most recent crisis by the range of some of the rockets launched from Gaza at Israel. Undoubtedly, Israeli intelligence surveillance and reconnaissance efforts already have identified some major storage and launch facilities and Qassam manufacturing points subsequently targeted by Israeli airpower. These efforts will continue. While it remains unclear whether this will suffice Israel's purposes, the 2006 conflict with Hezbollah in southern Lebanon left little doubt in the minds of the Israeli military about the limitations of airpower. The IDF probably will feel the need to enter Gaza on foot to root out more dispersed caches of rockets and supporting infrastructure. Israeli military action in Gaza naturally entails political consequences for Hamas. The main Palestinian Islamist movement since it won the 2006 Palestinian legislative elections has been having a hard time balancing its dual role as resistance group and governing party. It is trying simultaneously to function as a militant group fighting Israel and as a Palestinian government, first as the head of the Palestinian National Authority, and since June 2007 as the ruler of the Gaza Strip after its break and civil war with Fatah. Hamas knew that firing rockets into Israel even before its cease-fire with the country expired would give Israel reason to launch the current operation. But because Israel is not interested in reoccupying Gaza, a battered Hamas will have an even tougher time administering the area after the end of the Israeli operation, notwithstanding any surge in Hamas' popularity resulting from the assault. As long as Hamas and its allies cannot fundamentally threaten Israeli security, the Jewish state is happy to see the Palestinian territories divided between Hamas in Gaza and the militant Islamist group's secular rival, Fatah, in the West Bank. Another consequence of the Israeli raid is a deepening of the differences within Hamas. A natural outcome of the dual nature of the Islamist movement — both as an armed nonstate actor and as the ruling party in a protostate — is the division in the group between those more concerned about governance and those intent on maintaining the movement's original course, namely, militant opposition to the Jewish state. In recent years, there also has been a growing movement toward Salafism within Hamas, which has seen the rise of a more hard-core faction. This faction's influence over the armed wing of the group, the Izz al-Deen al-Qassam Brigades, has grown considerably. There are two fundamental dynamics to the current situation in play. The first is the degree to which Israel can succeed in eviscerating Hamas' military capability. The more successful Israel ultimately is, the longer Hamas remains a political entity without meaningful militant capability to back it up. Indeed, if Israel can meaningfully stave off the rocket fire for several years, Israel might be able to field counter -rocket, -artillery and - mortar systems capable of stymieing future Palestinian missile attacks. But second have been U.S. calls for Hamas to choose between politics and militancy. Whether Hamas' more pragmatic elements will gain an edge over the more ideological elements in the wake of the current offensive, or whether those radical Islamist elements will again rise to the fore in Hamas and the Gaza Strip, remains to be seen.