Russia’s invasion of Ukraine is approaching its fourth year. And as it drags on, Washington is learning just how vulnerable our nation could be in a similar conflict.

The glaring problem we now encounter is the erosion of our defense industrial base. The once vaunted arsenal of democracy that led America to victory in World War II is long gone. Simply put, we no longer produce the weapons and munitions needed for high-intensity, industrialized conflict.

Consider our startling inability to meet Ukraine’s need for 155-millimeter artillery rounds. It’s a key piece of weaponry in what has become an artillery and drone war. The Ukrainians sometimes fire as many as 8,000 rounds per day. The Russian army–with its vast Soviet-era reserve of weapons–regularly fires much more.

When the United States came to Ukraine’s aid, we started delivering as much 155-millimeter ammunition as possible. That quickly depleted stockpiles. We simply lacked the productive capacity to keep up with demand. At the start of the war, the United States was only producing 14,000 rounds a month–a mere two-day supply for Ukraine.

The U.S. Army has since invested billions of dollars to ramp up production. Three years later, we’re manufacturing 80,000 of these 155-millimeter rounds each month.

That’s still not enough. If the United States were directly involved in a conflict of this intensity–say with China–could we produce enough munitions to keep our troops supplied? It’s a deeply unsettling question.

We’ve lost both critical productive capacity and control of the supply chains needed to manufacture weapons and munitions. For example, supplies of materials and components for artillery rounds, drones, laser-guided bombs, and anti-drone systems are now stretched across the globe. A single munition can require as many as 500 suppliers from dozens of countries.

This is a crisis. China and other potential adversaries now control key pieces of our own defense industrial base–and it isn’t by accident. Beijing has taken control of the minerals used to manufacture a vast array of technologies including military hardware.

In response to new U.S. tariffs, Beijing just announced export controls on several key materials, including molybdenum and tungsten. This joins China’s other export restrictions announced in December on gallium, germanium, antimony, and other important minerals. This was done intentionally since these minerals are essential for military applications. China’s ban on antimony exports is particularly problematic since antimony is used in more than 300 types of U.S. munitions.

To the Trump administration’s credit, it has immediately focused on mineral security. President Trump has already ordered the Department of Defense to ensure that the National Defense Stockpile can provide “a robust supply of critical minerals in event of future shortfall.”

That’s an important first step. But America’s overreliance on mineral imports–particularly from China–is untenable. We need to rapidly start producing far more of these essential materials.

Ironically, the U.S. possesses vast mineral resources. But we’ve allowed our mining capacity to wither. Our dependence on antimony imports is a prime example. The U.S. even has a world-class antimony resource in Idaho. But a proposed mine there has waited years for approval–and may not begin production until 2028.

We need to vastly expand the U.S. National Defense Stockpile and the domestic mining capacity to feed it. Otherwise, any prolonged, high-intensity conflict could pose crippling problems.

The U.S. can learn much from the Ukraine war. But most important is the need to reinvest in America’s defense industrial base as soon as possible.

John Adams, U.S. Army Brigadier General (Retired), is president of Guardian Six Consulting and a former Deputy U.S. Military Representative to NATO’s Military Committee.