There has been much talk here in the last months (government ministers, military correspondents, etc on tv and radio) about various possible scenarios in which Israel would increase their military operations in Gaza (there have even been a couple small commando incursions into Gaza for specific targets such as Qassam launch pads) and acting on their threats to target Hamas PA ministers if terrorist attacks would occur. And, definitely, there have been many moves on many levels to pressure the collapse of the PA.
It's been obvious that the Israeli government/military (as if you can ever really separate the two) has been biding their time until they could use some incident a justification for some increased level of action.
For instance, Ha'aretz reports: "The detention of dozens of Hamas lawmakers in the early hours of Thursday morning had been planned several weeks ago and received approval from Attorney General Menachem Mazuz on Wednesday. The same day, Shin Bet Director Yuval Diskin presented Prime Minister Ehud Olmert with the list of Hamas officials slated for detention." (http://www.haaretz.com/hasen/spages/732528.html)
But I think that the scope of the Israeli response is somewhat of a surprise.
Moreover, there are two elements that are going to make this invasion problematic for Israel to justify among world opinion: The immediate trigger for the invasion and any understanding of proportionality.
Several months ago, Israeli Foreign Minister Tzipi Livni explicitly differentiated Palestinian guerrilla attacks against Israeli military targets from terrorist attacks against civilians. In an interview on the US Television news show ABC Nightline, recorded on March 28, 2006, Livni stated: "Somebody who is fighting against Israeli soldiers is an enemy and we will fight back, but I believe that this is not under the definition of terrorism, if the target is a soldier."
Even taking into consideration the large amount of tacit and explicit US and European governments backing of Israeli policies vis-a-vis the Hamas run PA, the Israeli government 'hasbarah' will have a harder time than usual trying to persuade international public opinion that the Palestinian guerrilla attack on the Israeli military position near the Kerem Shalom crossing point into Gaza, was, by any objective measure, a terrorist attack. Whether this will matter or not relates to how long the operation continues, how many casualties we see, whether or not the Palestinians reply with an attack on Israeli civilian targets inside the Green Line (which will then be used as a larger justification for the incursion after the fact), and how much noise you all make about it, etc...
On another level, I think that if you look at what triggered this huge Israeli military response, it says something significant about Israeli society, or at least the government's social scale of priorities. And perhaps even more importantly, it points to what really scares the Israeli government/military to act. Though there have been a number of attacks against civilian Israeli targets in recent times, be they the Qassam rockets or the recent bombing at the falafel stand near the old Tel Aviv central bus station (which killed 7 or so), it was not these which evoked such a disproportionate response. (First, obviously the extensive ongoing Israeli artillery barrages and assassinations, which have killed tens of civilians including many children, were disproportionate to say the least, but now we are talking about large-scale invasion with ground troops and tanks, plus the arrest and incarceration of 60 some Palestinian government ministers). It is only when an Israeli military target is hit, soldiers killed, and especially the capture of a soldier, that the Israeli gov/mil is energized into full-scale action. I can see two reasons here: One is that a successful attack on an Israeli military installation which was taken by surprise, is not just a specific isolated incident, a tactical setback, it is a spear shot deep into the spine of the Israeli ideological edifice that surrounds the institution of the military, a key component of the larger Zionist identity (or at least it sets up a fear of a crack in the edifice). The second reason (and I am sure there are others, but these come to mind), relates to the agreement that was being solidified between the Hamas and Fatah over the prisoner’s document. Among other elements, this would include the formation of a Palestinian unity government and an agreement to limit resistance to the Israeli occupation to the Occupied Palestinian Territories (OPT) (the territories occupied by Israel since 1967). While this would seem to be something that the Israeli establishment should recognize as a positive step forward, it is instead taken as a dangerous change that puts Israel’s interests in jeopardy. If the Palestinians shift their resistance solely to military targets or targets in the OPT, they lose their moral high ground (if Israel could really ever be seen to have one), lose the argument that the occupation must continue and the building of the Wall must continue, to secure the safety and defense of the Israeli civilian population. Even though there is speculation that the attack on Kerem Shalom was done as a way for the Palestinian militants to show that they would not agree to the stipulation of the agreement to not cross the Green Line (the military installation attacked was just over the border of Gaza in Israel), it still can be seen as significant that they focused on an explicitly military target instead of a civilian Israeli target. If a significant time-period passed in which only Israeli military targets and targets in the OPT would be hit, rumblings of pressure on Israel to move towards negotiations, move towards ending the occupation would potentially increase in frequency. This is a danger worth fighting against.
Whether or not the Israeli public are cheering the invasion and arrests on??? Well, the Israeli public are sheep by and by and will almost invariably back defense policy even if they have doubts, fears, critiques. From what I have been hearing, it seems that though a significant portion of the Israeli population thinks that something should be done, there is a lot of apprehension from them about re-entering Gaza, the fear that once in, we won’t come out, or fears of a relatively large amount of casualties as in the case of Jenin. Also fears remembering botched hostage ‘saving’ episodes such as in 1994. I think that the Israeli people’s willingness to back the incursion is related to how it pans out in the next week, how long the incursion goes on, number of casualties, etc…will determine the Israeli public’s mood.