Ever since Israel withdrew its soldiers and settlers from the Gaza Strip in 2005, critics have accused it of blockading and immiserating the territory — turning it, as Israel’s inveterate critics say, into an “open-air prison.”

The charge was always preposterous. Gaza shares a border with Egypt. The people of Gaza were often treated in Israeli hospitals for cancer and other life-threatening conditions. Israel provided Gaza with much of its electricity and other critical goods even after Hamas came to power in 2007.

Now, as Israeli troops uncover more of Gaza’s vast underground city, the falsity of the accusation has become even more apparent.

According to a report this month in The New York Times, Israeli defense officials now estimate that Hamas’ tunnels measure between 350 and 450 miles in a territory that’s just 25 miles long. (By comparison, the London Underground is only 249 miles long.) Some of Gaza’s tunnels are wide enough for cars; some are more than 150 feet deep; some serve as munitions depots; others are comfortably kitted out as command bunkers.

Israeli officials also estimate that there are 5,700 separate entrances to the tunnels — many of them with access from civilian houses and some directly beneath Gaza City’s main hospital, which U.S. intelligence agencies say was also used as a Hamas command center. Within that maze, scores of Israeli hostages, including a year-old infant, are being held without fresh air, sunlight, adequate medicine or food, or visits from the Red Cross.

All this should radically reconfigure the world’s understanding of what Hamas has done in, and to, Gaza. It has turned the territory into a gigantic military fortress purpose-built to attack Israel, endure Israeli retaliation and interpose civilian lives and infrastructure as part of its means of defense. Imagine any other government doing something similar to its people — say, putting the NORAD command center directly below Times Square — for a sense of the outrage Hamas is perpetrating against its own people.

That’s not the only outrage. How much did it cost to build these tunnels? How much concrete, steel and electricity did it divert from civilian needs? How many millions of hours of labor were given to the effort? What was the cost of building up its stockpile of thousands of rockets, which continue to be fired at Israel? How many ordinary Gaza civilians had to be conscripted into the effort of miserably shoveling dirt deep underground — and how many perished in the effort?

We may never know for sure. But in 2014, around the time Israel first started to get a sense of the scale of Hamas’ tunnel network, The Wall Street Journal, citing Israeli military officials, reported that the cost of building 32 tunnels (a small fraction of what has since been uncovered) came to around $90 million.

“Some tunnel-building materials also came from aid earmarked for development projects by international aid agencies in Gaza or were purchased on the open market when Israel allowed some imports into Gaza starting in 2010,” the Journal added.

In other words, Hamas stole from foreign donors, subtracted what probably amounted to billions of dollars over several years from Gaza’s gross domestic product, and diverted labor from productive to destructive ends, all to feed its war machine. Western progressives are usually against this sort of thing, at least when it comes to the guns-to-butter ratio in their own democracies. Why are they virtually silent about it now?

The tunnels also help explain the level of destruction that Israel has wreaked on Gaza since the war began. If Hamas hides the bulk of its fighters and munitions in the tunnels, Israel somehow has to find, search and destroy those tunnels. If Hamas builds the entrances to those tunnels inside private homes, schools or hospitals, those places all become military targets.

And if there are nearly 6,000 such entrances, the destruction is all but guaranteed to be epochal — just as it was in Mosul when the United States assisted Iraq in destroying the Islamic State group (which was much less deeply entrenched there than Hamas is in Gaza) over nine months in 2016 and 2017. I don’t recall “Cease-Fire Now” demonstrations on college campuses back then.

It’s possible that Israel could fight with more discrimination to spare Palestinian lives while still destroying Hamas’ ability to make war. If so, it behooves Israel’s constant critics to explain precisely how, and to do so in a way that doesn’t let Hamas off the hook. Otherwise, the tragic reality of this war is that it is going to be catastrophic for Gaza — not because Israel wills it, but because Hamas spent years of cynical efforts to make it so.

Hamas could have averted this tragedy if it had turned Gaza into an enclave for peace rather than terror. It could have averted it if it had not started four previous rounds of war against Israel. It could have averted it if it had honored the cease-fire that held on Oct. 6. It could have lessened the blow against the people of Gaza by fighting in the open, not behind civilians. It could have eased it by releasing all of its hostages. It could end it now by surrendering its leaders and sending its fighters into exile.

Till then, something I wrote in October holds true now: Hamas bears the blame for every death in this war.

Bret Stephens writes a column for the New York Times.