They’ve been holding off, partly to give Egypt time to try to broker a truce and partly because they know escalation will make the true believers in Cairo scream even more loudly about tearing up the treaty. But no truce is in the offing right now and they’re not going to sit by while Tel Aviv and Jerusalem(!) are targeted. So here we go:

Defense Minister Ehud Barak approved the IDF’s request on Friday evening to increase the maximum number of reservists it could enlist, seeking cabinet approval to mobilize up to 75,000 troops ahead of a possible Gaza ground operation.

The Inner Cabinet, a group of nine senior ministers, met for over three hours to discuss the possibility of a ground operation into the Hamas-controlled enclave, but released no statements or indications as to what transpired during the meeting…

The IDF also revealed on Friday that it had taken out Hamas’s nascent drone program.

Israel’s foreign minister ruled out regime change as a strategic goal (this time) so their top priority presumably is to seek and destroy Hamas’s remaining Iranian-made long-range missiles. One thing I don’t understand, though: Why now? Why did Hamas choose this moment to ramp up rocket attacks and try to bait Israel into a more extended confrontation? Normally that question begins by assessing the motives of their patron, Iran, and their pals in Egypt, but it’s not obvious to me how either of those countries benefit significantly from a short Gaza conflict right now. Hamas isn’t going to degrade Israeli air power needed for a strike on Iran’s nuclear facilities and a war in Gaza won’t go on long enough to substantially delay an Israeli attack on Iran if one’s in the offing. In Egypt, the Muslim Brotherhood wants a confrontation with Israel eventually but probably not just yet; a new war and humiliating defeat would crush their ambitions a year after taking power, and Morsi’s grip on the military probably isn’t firm enough yet to guarantee that the army will support a new conflict with the IDF.

So why is Hamas doing this? Is it something ordered on their own initiative, maybe to pressure Morsi into supporting them full-throatedly? (If so, it’s working. He just sent his PM to Gaza for a courtesy call with Hamas.) Is the JPost right that this is actually some sort of morale-building exercise by Hamas after Israel liquidated terror capo Ahmed Jabari? Or is there a political calculus aimed at Israeli civilians?

Netanyahu is favorite to win a January national election, but further rocket strikes against Tel Aviv, a free-wheeling city Israelis equate with New York, and Jerusalem, which Israel regards as its capital, could be political poison for the conservative leader…

Asked about Israel massing forces for a possible Gaza invasion, Hamas spokesman Sami Abu Zuhri said: “The Israelis should be aware of the grave results of such a raid, and they should bring their body bags.”

Undermine Netanyahu’s security credentials by threatening Jerusalem or by turning an invasion of Gaza into a fiasco and a more dovish candidate might benefit in Israeli elections. The only problem with that theory? Arguably, this is in fact a perfect time for Israel to tackle Hamas:

For months Israel has been determined to take steps to show that it would defend its interests.

The U.S. very publicly demanded restraint from Israel in terms of the Iranian nuclear program and would not commit to providing the backing several analysts say that Israel would need to make the operation successful. So Israel backed off from its loud threats to Iran, for now.

Chaos in Syria spilling over into Lebanon in the form of a devastating car bombing has forced Iranian proxy Hezbollah to focus on keeping Assad in power and taking out targets within Lebanon, rather than striking Israel.

So Gaza is the only obvious target remaining, and direct conflict in the form of Palestinian rocket attacks and Israeli strikes have grown increasingly intense and frequent as the year has progressed.

With Jabari and several other Hamas leaders dead and the IDF hard at work on pulverizing their missile depots, Netanyahu’s probably boosted his reelection credentials at this point. But that’s what makes the mobilization of reserves and possible ground operations surprising. He must think they’re absolutely necessary to liquidate Hamas’s remaining arsenal if he’s choosing not to quit while he’s ahead politically.

The latest news, by the way: Rockets have allegedly been fired into Israel from … the Sinai. If I were you, I’d take five minutes to read David French’s post from yesterday about how the rules of war govern a conflict in Gaza. You’ll be hearing a lot of disinformation about this next week if the IDF does end up going in.

Update: Invasion is no easy business.