“To be prepared for war,” George Washington said, “is one of the most effectual means of preserving peace.” President Ronald Reagan agreed with his forebear’s words, and peace through strength became a theme of his administration. In the past four decades, the American arsenal helped secure that peace, but political neglect has led to its atrophy as other nations’ war machines have kicked into high gear. Most Americans do not realize the specter of great power conflict has risen again.

It is far past time to rebuild America’s military. We can avoid war by preparing for it.

When America’s senior military leaders testify before my colleagues and me on the U.S. Senate Armed Services Committee behind closed doors, they have said that we face some of the most dangerous global threat environments since World War II. Then, they darken that already unsettling picture by explaining that our armed forces are at risk of being underequipped and outgunned. We struggle to build and maintain ships, our fighter jet fleet is dangerously small, and our military infrastructure is outdated. Meanwhile, America’s adversaries are growing their militaries and getting more aggressive.

In China, the country’s leader, Xi Jinping, has orchestrated a historic military modernization intended to exploit the U.S. military’s weaknesses. He has overtaken the U.S. Navy in fleet size, built one of the world’s largest missile stockpiles and made big advances in space. President Vladimir Putin of Russia has thrown Europe into war and mobilized his society for long-term conflict. Iran and its proxy groups have escalated their shadow war against Israel and increased attacks on U.S. ships and soldiers. And North Korea has disregarded efforts toward arms control negotiations and moved toward wartime readiness.

Worse yet, these governments are materially helping one another, cooperating in new ways to prevent an American-led 21st century. Iran has provided Russia with battlefield drones, and China is sending technical and logistical help to aid Mr. Putin’s war. They are also helping one another prepare for future fights by increasing weapons transfers and to evade sanctions. Their unprecedented coordination makes new global conflict increasingly possible.

That theoretical future could come faster than most Americans think. We may find ourselves in a state of extreme vulnerability in a matter of a few years, according to a growing consensus of experts. Our military readiness could be at its lowest point in decades just as China’s military in particular hits its stride. The U.S. Indo-Pacific commander released what I believe to be the largest list of unfunded items ever for services and combatant commands for next year’s budget, amounting to $11 billion. It requested funding for a raft of infrastructure, missile defense and targeting programs that would prove vital in a Pacific fight. China, on the other hand, has no such problems, as it accumulates the world’s leading hypersonic arsenal with a mix of other lethal cruise and attack missiles.

Our military leaders are being forced to make impossible choices. The Navy is struggling to adequately fund new ships, routine maintenance and munition procurement; it is unable to effectively address all three. We recently signed a deal to sell submarines to Australia, but we’ve failed to sufficiently fund our own submarine industrial base, leaving an aging fleet unprepared to respond to threats. Two of the three most important nuclear modernization programs are underfunded and are at risk of delays. The military faces a backlog of at least $180 billion for basic maintenance, from barracks to training ranges. This projects weakness to our adversaries as we send service members abroad with diminished ability to respond to crises.

Fortunately, we can change course. We can avoid that extreme vulnerability and resurrect American military might.

On Wednesday I am publishing a plan that includes a series of detailed proposals to address this reality head-on. We have been living off the Reagan military buildup for too long; it is time for updates and upgrades. My plan outlines why and how the United States should aim to spend an additional $55 billion on the military in the 2025 fiscal year and grow military spending from a projected 2.9 percent of our national gross domestic product this year to 5 percent over the next five to seven years.

It would be a significant investment that would start a reckoning over our nation’s spending priorities. There will be conversations ahead about all manner of budget questions. We do not need to spend this much indefinitely — but we do need a short-term generational investment to help us prevent another world war.

My blueprint would grow the Navy to 357 ships by 2035 and halt our shrinking Air Force fleet by producing at least 340 additional fighters in five years. This will help patch near-term holes and put each fleet on a sustainable trajectory. The plan would also replenish the Air Force tanker and training fleets, accelerate the modernization of the Army and Marine Corps, and invest in joint capabilities that are all too often forgotten, including logistics and munitions.

The proposal would build on the $3.3 billion in submarine industrial base funding included in the national security supplemental passed in April, so we can bolster our defense and that of our allies. It would also rapidly equip service members all over the world with innovative technologies at scale, from the seabed to the stars.

We should pair increased investment with wiser spending. Combining this crucial investment with fiscal responsibility would funnel resources to the most strategic ends. Emerging technology must play an essential role, and we can build and deploy much of it in less than five years. My road map would also help make improvements to the military procurement system and increase accountability for bureaucrats and companies that fail to perform on vital national security projects.

This whole endeavor would shake our status quo but be far less disruptive and expensive than the alternative. Should China decide to wage war with the United States, the global economy could immediately fall into a depression. Americans have grown far too comfortable under the decades-old presumption of overwhelming military superiority. And that false sense of security has led us to ignore necessary maintenance and made us vulnerable.

Our ability to deter our adversaries can be regained because we have done it before. At the 50th anniversary of Pearl Harbor, in the twilight of the Soviet Union, George H.W. Bush reflected on the lessons of Pearl Harbor. Though the conflict was long gone, it taught him an enduring lesson: “When it comes to national defense,” he said, “finishing second means finishing last.”

Regaining American strength will be expensive. But fighting a war — and worse, losing one — is far more costly. We need to begin a national conversation today on how we achieve a peaceful, prosperous and American-led 21st century. The first step is a generational investment in the U.S. military.

Roger Wicker is a U.S. senator for Mississippi and serves as the ranking member of the Senate Armed Services Committee.