The F-35 fighter jet is one hell of a flying machine.

Stealthy. Supersonic. Stuffed with computers, sensors and electronics that would have looked like science fiction to the guys flying Phantoms over Vietnam.

But park one on the ramp, shut down the engine and forget the Pentagon sales pitch for a minute.

Look at what it’s made of.

Aluminum. Titanium. Copper. Cobalt. Rare earths. Magnets. Electronics.

And none of that stuff begins life at Lockheed Martin.

It begins in the dirt.

Somebody has to find it.

Somebody has to dig it up.

Somebody has to refine it.

Somebody has to turn it into something an American factory can use.

Only then can somebody build the parts that eventually become a $100-million fighter.

For decades, America somehow managed to forget that little detail.

We became very good at buying the finished weapon and increasingly dependent on somebody else for the industrial guts required to build it.

That’s a lousy way to prepare for a war.

Apparently somebody at the Pentagon finally figured that out.

This week, the Defense Department announced a series of investments that aren’t particularly sexy. No new fighter. No shiny destroyer. No missile screaming off a launch rail for the cameras.

Mines and refineries.

And Uncle Sam isn’t merely buying what they produce.

He’s buying pieces of the companies.

On Friday, the Pentagon announced a $35.6 million strategic equity investment in Trilogy Metals. The government gets a 10-percent stake in the company, plus warrants that could increase its economic interest.

Trilogy is tied to Alaska’s Upper Kobuk mineral projects.

Copper.

Cobalt.

Germanium.

The sort of stuff nobody talks about at an air show, but everybody starts worrying about when the supply stops.

The Pentagon also put another $100 million into Atalco, bringing the government’s investment there to $400 million.

Atalco operates the Gramercy refinery in Louisiana.

Here’s the part that ought to make somebody spill his morning coffee:

It is the last operating alumina refinery in the United States.

One.

The United States has 11 nuclear-powered aircraft carriers. Thousands of military aircraft. Nuclear submarines. Satellites. Missiles. Drones.

And one domestic alumina refinery.

That’s not an industrial base.

That’s a single point of failure with an American flag hanging over it.

A few days earlier, Washington announced another $750 million investment involving Serra Verde’s rare-earth operation in Brazil. Add the Defense Logistics Agency purchase commitment and private financing and the package reaches $1.55 billion.

Serra Verde produces the wonderfully named neodymium, praseodymium, dysprosium and terbium.

Don’t worry about pronouncing them.

Just worry about getting them.

They help make the high-performance magnets and components used throughout modern military technology.

And China has spent decades making sure much of the world depends upon Chinese-controlled supply chains for critical minerals and processing.

Beijing understood something Washington forgot. The weapon doesn’t begin at the assembly plant. It begins at the mine.

That lesson shouldn’t require a Ph.D. from the War College.

Ask any old mechanic.

You can have the finest machine in the world sitting in the motor pool, but if you can’t get the part that makes the damn thing run, you’ve got a very expensive lawn ornament.

An F-35 isn’t much different.

Neither is a Virginia-class submarine.

Neither is a Tomahawk missile.

Neither is a satellite.

We spent decades admiring the spear while somebody else was making the steel.

Now Washington is trying to fix it.

Uncle Sam has become a shareholder.

We’ve seen government ownership before. Washington has rescued companies during economic crises. It owned a huge chunk of General Motors after the 2008 financial collapse. The federal government owns Amtrak.

But this is different.

Nobody is rescuing Trilogy because America’s financial system will collapse if the stock goes to zero.

The Pentagon wants a piece of Trilogy because what’s underneath the ground matters to national security.

That’s an important distinction.

It also has a very old-fashioned American precedent.

During World War II, Washington understood perfectly well that you couldn’t defeat Germany and Japan by ordering airplanes from factories that didn’t exist.

So America built factories.

Aluminum plants.

Shipyards.

Machine shops.

Synthetic-rubber plants.

The government financed industrial capacity because industrial capacity was part of national defense.

The Arsenal of Democracy required an arsenal.

What we’re seeing now looks like a modern version of the same thinking.

Washington isn’t nationalizing the mines.

It isn’t putting some lieutenant colonel behind the desk at the Gramercy refinery.

Instead, the government is putting capital into strategically important companies and receiving an ownership interest in return.

There is something refreshingly sensible about that.

If taxpayers are putting up the money, taxpayers ought to get something besides a press release.

If the company succeeds, Uncle Sam owns an asset.

If production expands, America gets another supply source.

And if somebody overseas decides to turn off the tap during a war, we’re not standing around wondering where the next shipment went.

But keep one hand on your wallet.

Anytime Washington discovers a new pot of money, somebody discovers a reason he deserves some of it.

Mining companies will hire lobbyists.

Congressmen will discover strategically vital minerals conveniently located in their districts.

And pretty soon somebody will undoubtedly produce a 400-page study explaining why taxpayers urgently need to invest $600 million in a mine containing something nobody had heard of.

So Congress needs to watch this program.

Every investment should answer three questions:

• Does the military actually need the material?
• Is the supply chain genuinely vulnerable?
• And does putting taxpayer money into this company make America less dependent upon a potential enemy?

If the answers are yes, write the check.

Because there’s another price that’s considerably higher.

Going to war and discovering you can’t replace what you’re shooting, flying or sailing.

The Pentagon has spent generations worrying about how many fighters, ships and missiles America can buy.

Maybe somebody finally asked the more important question:

How many can we build after the first ones are gone?

That’s where mines and refineries stop being boring industrial policy and start becoming national defense.

An F-35 may cost nearly $100 million.

But before anybody builds one, somebody has to dig a hole.

And you’d damn well better make sure it’s our hole—or one belonging to a friend.