As with commentary on the Russia-Ukraine war, I should note I have been out of the field of security studies for many years, and therefore am not a true expert, though I do have some familiarity with Israel (where I have relatives and other contacts), its politics, and its security issues (which I did do some work on back in the day). What follows may not be worth much more than what you're (not) paying for it! Still, here goes:
As many of you know, I have lots of objections to Israeli government policy generally, and the current right-wing government in particular. Nonetheless, Israel has a just cause in this conflict, and Hamas does not. As with Russia and Ukraine, there is a vast moral chasm between the two sides, and it does not favor the one that is a medieval theocracy that deliberately terrorizes civilians and takes them hostage.
The Palestinians have some legitimate grievances against Israel, and I am not in principle opposed to a Palestinian state. But I see no reason to support establishing one that would be either a brutal Islamist theocracy (Hamas), or a corrupt dictatorship (the Palestinian Authority). A regime like Hamas's, especially, has no legitimate claim to rule anyone or anything.
What happened today was a spectacular intelligence failure by Israel's vaunted security establishment - the worst since the Yom Kippur War (almost exactly 50 years ago). Not clear why it happened (people will argue about it for years). But perhaps they became complacent, as also happened in 1973. Maybe they just didn't think Hamas could or would attack on such a scale, and interpreted the evidence to fit that predisposition (a similar error underlay the 1973 failure).
Bibi Netanyahu's right-wing government likely bears a hefty share of blame for what happened here. Their assault on the judiciary and other divisive policies weakened the military (as military leaders warned), and clearly led Israel's enemies to sense weakness (as those enemies themselves have said). Ironically, Bibi's platform in the 2022 election heavily emphasized his credentials on national security, which he claimed the previous government had neglected.
While I have not yet had a chance to talk to friends and relatives in Israel, I think we cannot underestimate the impact of today's events there. The 250 dead recorded so far - most of them civilians - is a far larger proportional death toll (relative to population) than what the US suffered on 9/11. Expect a similarly massive reaction - or so I expect. And the toll will probably have gone up by the time you read this.
Despite it's inexcusable failures today, the Israeli military is ultimately far stronger than Hamas. Mark my words: they will win. The only question is how big a victory will they seek. Will they "merely" inflict massive losses on Hamas and reoccupy part of the Gaza Strip, or will they seek to overthrow Hamas entirely? Either is possible, I think.
Bibi's political calculations are also relevant to the previous point. He is in danger of suffering the fate of Gold Meir (the Israeli PM who fell from power after she presided over the surprise attack of the Yom Kippur War). If he's going to avoid becoming a right-wing version of Golda, he has to win big! That may tilt him towards crushing Hamas completely, though a countervailing factor is that doing so means a longer fight with more casualties.
Opposition leaders Yair Lapid and Benny Gantz have offered Bibi a broad coalition government in exchange for his dumping his more egregious current right-wing allies. I hope he takes the deal, though I am skeptical it will happen.
Unless I have things totally wrong (always a possibility!), expect a massive Israeli ground operation in Gaza within the next few days.
I worry that this war will divert US attention way from the Ukraine conflict. There is no reason why we can't support both Ukraine and Israel. The Israelis don't need much in the way of weapons or logistical support. They can fend for themselves, and need only our diplomatic backing. Republicans who say we should dump Ukraine to better back Israel are offering a false choice. We can prevail on both fronts with only modest investments of US resources (barely a rounding error in the federal budget), though the costs to those directly involved in the conflicts are obviously far higher (but both Ukrainians and Israelis are willing to pay them, because they know the alternatives are worse).
Much more can be said. But this is enough - perhaps more than enough - for now. For what little value it may have, I extend sympathy and support to Israelis who may read this post.