Opinion Editorials

As he assumes the awesome responsibilities of the presidency, Donald Trump has inherited a world on fire and a U.S. military weakened by years of senseless budget cuts. I am encouraged that he recognizes these problems and has pledged to rebuild the military. The work to get the armed forces back up to speed must begin now. 

The world order America has led since the end of World War II—which has benefited the American people most of all—is now under unprecedented strain. The U.S. has entered an era of great-power competition, even as it continues to face an enduring conflict against Islamist extremist groups. 

Yet many Americans have forgotten that the world order is not self-sustaining. Not all threats have purely military solutions, but they all have military dimensions. Hard power matters: It is what gives the U.S. leverage to deter aggression and achieve peace through strength. 

The Budget Control Act of 2011, which cut and arbitrarily capped military spending for a decade, epitomizes this country’s forgetfulness about its role in the world. The provision, known as the “sequester,” was designed to be so harmful to the military that Congress would be forced to enact reforms to control federal spending. Reforms never came, so the cutting and capping of military spending did. The military has paid a terrible price.

From 2010 through 2014, the defense budget was cut by 21%, according to analysis from the Center for Strategic and Budget Assessments. Across the board, the military got smaller and less capable. Critical investments in new technologies were deferred, which helped adversaries like Russia and China close the gap. The combination of rising threats, declining budgets, aging equipment, shrinking forces and high operational tempo has produced a military readiness crisis.

President Trump is now commander in chief of a military that is underfunded, undersized and unready to meet the diverse and complex array of threats confronting our nation. That is why every member of the Joint Chiefs of Staff has testified to Senate Armed Services Committee that years of budget cuts have placed the lives of the men and women of our armed forces at greater risk. 

President Trump has committed to eliminating the defense sequester and rebuilding the military. I fully agree, and we need to get started right away. There are two main tasks. 

The first is modernizing the military for the new realities of deterring conflict and competing with great powers that possess advanced capabilities. For too long, the U.S. has taken for granted that its forces could operate anywhere and dominate any environment with minimal effort. That assumption no longer holds. However, with greater investments in technology such as hypersonic munitions and artificial intelligence, the military can become much more capable over the next five years. 

The second priority is regaining capacity for the military to perform its current missions at acceptable levels of risk. Today the armed forces simply do not have enough ships, aircraft, vehicles, munitions, equipment and personnel. Adding capacity alone is not the answer, and increasing capacity, especially personnel, must be done deliberately and sustainably. But this is a yearslong process that should begin immediately. 

The military has to become not only bigger but more efficient. There is room to cut wasteful spending at the Defense Department. And patience remains important: The harm that has been done to the military over eight years will not be reversed quickly. But the longer the wait, the longer it will take to reform. 

This won’t come cheap. It will require a base defense budget for fiscal year 2018, excluding current war costs, of $640 billion. That’s $54 billion above current plans, and sustained growth will be required for years thereafter. Defense is the country’s No. 1 priority. It must be a political priority on par with repealing and replacing ObamaCare, investing in public-works projects, and reforming the tax code. 

I was a humble foot soldier in the Reagan Revolution. The 40th president is remembered as one of the greatest because he embraced his role as commander in chief, rebuilt America’s military and secured peace through strength. President Trump has a similar opportunity. If he is committed to seize that opportunity, I will be a committed partner in that effort.

Mr. McCain, a Republican from Arizona, is chairman of the Senate Armed Services Committee.