The NYT quotes the U.N. Secretary-General saying this (regarding the Hamas "pillage and murder" raids in Southern Israel):  “Nothing can justify these acts of terror and the killing, maiming and abduction of civilians.”  This seems like a rather good principle, even if it is unsatisfying to those who think, "No it is justified against an apartheid state" or "It is justified by the way Israel has treated the Palestinians" and so on.  The reason the principle should be treated as an absolute is obvious:  in the absence of such a norm, the scale of human misery during conflict and war will be far greater than it already is.   When Israel invades Gaza, there will be, correctly, demands that it observe that norm, even if the Hamas barbarians did not.  We saw what happened in WWII when that norm was rarely observed.  We need it to hold, and those who violate it deserve to become pariahs.

Regarding the invasion of Gaza, this opinion piece suggests, not implausibly, that this may have been exactly what Hamas wanted as part of its longterm strategy:

Hamas knew that the attack on Saturday would give Mr. Netanyahu little choice but to retaliate with a ground invasion, and it knows that Israel Defense Forces technology and military superiority will offer little advantage on the crowded streets of Gaza City, in Jabalia, Gaza’s largest refugee camp, or through Hamas’s labyrinth of underground tunnels…

It appears Hamas wants to draw Israeli soldiers into a quagmire, like Hezbollah did in Southern Lebanon from 1985 to 2000. After years of fighting, Israel suffered a humiliating and chaotic withdrawal, leaving an empowered and threatening Hezbollah on its northern border.

Why might Hamas want to draw the I.D.F. into a bloody ground battle? Hamas is the uncontested power in Gaza, though elections have not been held since 2006. Neither the Palestinian Authority nor its main political party, Fatah, the business community, civil society nor family clan leaders can effectively challenge Hamas, which has become only stronger after each successive conflict with Israel….Hamas surely believes it can defeat the Israelis on its home turf in a war of attrition.

Hamas also stands to expand its political credibility in the West Bank if Israel invades Gaza, particularly if Israeli advances stall. Many Palestinians in the West Bank already regard the Palestinian Authority, which administers parts of the Israeli-occupied West Bank, as corrupt, enfeebled and unable to realize the aspirations of its people. Israel’s July incursion into the West Bank city of Jenin further highlighted that the government of the president of the Palestinian Authority, Mahmoud Abbas, can neither protect the people of Jenin nor provide a vision of a more hopeful future. If Israel invades Gaza, Hamas may have the public support to challenge the Palestinian Authority in the West Bank and potentially assume leadership as the sole representative of the Palestinian people.

In the broader region, Hamas can also count on its ally, Hezbollah. The day after the Hamas attack in southern Israel, Hezbollah, presumably in an attempt to test the readiness of Israeli forces, engaged in fighting with the Israeli military along the northern border near Shebaa Farms, land that is controlled by Israel but claimed by Lebanon. Hezbollah may seek to gain further advantage if Israel is fighting Hamas in Gaza and the West Bank.

Recall that hundreds of thousands of people in Gaza do not support Hamas, and have nothing to do with it.  This Washington Post piece by a Gaza citizen is revealing:

I’m heading off to the school where I teach. The car arrives to pick me up. My 7-year-old daughter, Yaffa, is leaving to wait for her school bus. Suddenly, a rocket shoots across the sky.

My wife tries to reassure me: “It’s just a test. They’re firing toward the sea.” She could be right. That sometimes happens even during “peaceful” times. But then another rocket takes off, this time definitely heading for Israel. Then more rockets, flying from all directions.What we don’t know is that dozens of militants from Gaza have infiltrated Israeli towns near the border. Only around two hours later do we begin to see a flood of photos and videos of Gaza militants killing soldiers and civilians and taking others as prisoners. No one can believe their eyes.

My brother-in-law, Mohammed, drives by. “Does anyone want to go to the market?”

At times like these, our first thoughts immediately turn to essential supplies. Bread is at the top of the list. Even if there’s flour, electricity is likely to be cut for long hours, so it will be hard to bake at home.

We set out for a shopping center. I manage to buy some chicken and cucumbers and avocados, but dozens of people are queuing for bread, pushing and fighting. The owner shuts the doors. We decide to try somewhere else….

We can’t find any bread, so we return home with only the chicken and avocados and cucumbers.

The images of dozens of Israeli casualties and prisoners haunt me. How did the militants cross such a closely monitored border? How could they kill all these soldiers and take so many others as prisoners? You can only assume that Israel will kill hundreds, even thousands, of civilians in Gaza. I’ve never felt so terrfied.

We hear Israeli Prime Minister Benjamin Netanyahu’s statement that the people of Gaza should “leave now.” I find myself asking: “Where are we supposed to go? Didn’t our grandparents leave their houses in 1948?”