Most of this is just interpretation of recent comments by Graham and Mattis. But if you read to the end, there is a sinister hypothesis of North Korea intentions.

If Lindsay Graham is correct, Trump has crossed a mental Rubicon, the river of no return. Quoting (CNN) Lindsay Graham,

“You’re making the President pick between regional stability and homeland stability,” Graham said on “Today.” “There will be a war with North Korea over the missile program if they continue to try to hit America with an ICBM. (Trump has) told me that. I believe him.”

In the road to commit, the choice between U.S. security, and the costs incurred by others, particularly South Korea, has the greatest moral difficulty . If Graham is correct, Trump has surmounted this mental obstacle. The chief remaining obstacle is given by General Mattis,  in his statement that this would be the worst war we’ve seen since 1953. With Vietnam to compare, this is quite a statement.

So why can’t this be an air war, or a surgical intervention? North Korea’s missile industry/deployment complex is extensively hardened, buried in the mountainous terrain. A “mow the grass” strategy is possible, which would involve slowly digging out, or merely degrading the complexes as they become discoverable. This low intensity approach would be of indefinite duration. But two factors go against the lower intensity options.

Massive quantities of artillery are embedded in the mountains north of the DMZ, within range or partial range of Seoul. For decades, these guns have been the stuff of myth. They were formerly thought to be huge in number. They were impregnable except to counter battery fire,  When a gun fires, the projectile is tracked on radar, disclosing the gun position to retaliation, either by modern precision weapons, or by precisely aimed artillery. But the digging out process takes time, too slow, according to the myth, to prevent the flattening of Seoul.

More  recently, studies (see Nautilus) have replaced the myth with a a much smaller assessment of the damage these guns can do. But this is cold comfort. Mattis knows that unless the gun emplacements are physically occupied, the North Koreans will replenish the positions, and shell Seoul indefinitely.

And missiles, or other aerial methods are not the only way a rogue state can deliver. George Tenet fears unconventional delivery of nuclear weapons. I wrote about it in North Korea’s Plutonium, Iran’s Uranium / Suitcase Nukes. Aside from Tenet and myself,  the suitcase nuke is widely thought to be a myth. Or if they once existed, they have aged to the point of non functionality. But North Korea is in a unique position to refurbish them.

This increases concern related to: (CNN) US detects ‘highly unusual’ North Korean submarine activity’.  Quoting,

US officials also noted that a North Korean Sang-O submarine was operating in the Yellow Sea and the length of its deployment was notable. Two Romeo submarines were detected in the waters off Japan — each one operating in the area for about a week….

and

Carried out on land at Sinpo Naval Shipyard, Sunday’s ejection test is the third time this month — and fourth this year — that North Korea has conducted a trial of the missile component that is critical to developing submarine launch capabilities, according to the US defense official.

The ejection tests could be in the service of missile development, but could have an immediate sinister purpose. Ultimately, it doesn’t matter how a nuclear device arrives at a target. Whether it is North Korea indigenous or suitcase refurb, It can be driven, smuggled, shipped, dropped in  the ocean and left to drift, or given it a little motor to help it along. It can be covered to make it look like flotsam. A missile tube is a very convenient way to deploy such a floating device from a submarine.

The opinion of General Mattis that this would be a serious conflict is likely related to this concern. While “mowing the grass”, or targeting infrastructure would frustrate further technological progress by North Korea, it would also create a festering desire by North Korea to blackmail, or for unsymmetrical retaliation, including the unconventional delivery of nuclear weapons.

This  prioritizes land occupation, for thorough accounting and destruction of nuclear facilities and materials. And this is likely why Diane Feinstein said,

“My reaction is that Lindsey Graham should get a classified briefing like the ones I have had,” the California Democrat told MSNBC’s Andrea Mitchell. “It is all classified. But we know much more about these weapons and where they are. And what the difficulties are. That’s all I can say.”

Feinstein likely learned that not everything can be hit from the air. Some things are buried too deep.  A nuclear reactor cannot be hit from the air once in operation, because of the likelihood of large releases of radioactive substances.

There certainly exist unconventional or nonlinear  possibilities that could change this fight into something less awful.   But we must assume the worst.

From Time Magazine:

When Dwight D. Eisenhower was Supreme Commander of the Allied Forces during World War II, he met with paratroopers of the 101st Airborne Division in order to boost morale as D-Day drew ever closer. He must have known that the odds were stacked against his men — indeed, he expected the casualty rate for the 101st Airborne to run as high as 70%. “I’ve done all I can,” he’d told them. “Now it is up to you.” Later, as reported in Michael Korda’s biography Ike: An American Hero, Eisenhower stood on the roof of the nearby headquarters, with tears in his eyes, saluting each and every plane as it left for France.

I would like to say to General Mattis something like, “I share you pain.” But it’s impossible. For him, it’s personal.