The Constitution focuses primarily on limiting the power of the federal government. The founders knew that most things can be done more effectively and efficiently at the state level, or simply by the people themselves.

But one of the few powers they gave Washington is the responsibility to provide for the security of the United States. It takes the federal government to effectively defend our nation and our vital national interests abroad.

Unfortunately, as of 2015, Washington appears disturbingly cavalier about meeting this responsibility. America's military grapples with shrinking force size, rocketing costs, and outdated equipment.

A new measure of our national defense capabilities released by The Heritage Foundation, The Index of U.S. Military Strength, reveals several areas of weakness and geopolitical uncertainty that demand our attention.

The Index is an objective analysis which, among other considerations, judges our military strength by the "two major regional contingency requirement" - the capability to handle two major wars at the same time. America must be able to engage an enemy in one part of the world without creating an opportunity for another enemy to threaten the U.S. and her interests elsewhere.

Of the four branches of our armed services, three, plus our nuclear capability, were found to be "Marginal" - right in the middle of a scale from "Very Weak" to "Very Strong." Only our Air Force was rated "Strong." This is in the face of "Elevated" threat levels to vital U.S. interests from Iran, the Middle East and North Korea, and "High" threats from an annex-happy Russia and a rising China.

The Index also highlights the continuing challenges of asymmetric war and terrorism by the Islamic State, and continual cyber-attacks originating from China, Russia and Iran. Overall, our military capabilities in the current environment are rated "Marginal," meaning the Armed Forces are up to the task of a single major conflict and attendant global duties, but would be severely strained in tackling multiple fronts.

Incredibly, no one has conducted an annual, systematic review of America's defense capabilities - relative to threat - until now. Heritage's Index fills this shortfall, and its revelations should concern Americans of all political stripes, even those who reasonably object to past or current foreign policy. We don't need to always be at war to always be prepared for war.

Regrettably, our military's current deficiencies are consistent with the "Obama Doctrine" of foreign policy: America as an "equal partner" with other nations instead of an exceptional world leader. This isn't just misplaced modesty on the president's part. It is willful dismissal of historical and present reality of American leadership, and turns a deaf ear to our allies across the world, who look to America for support against bullying neighbors and rogue states.

The fact that our military's ability to defend America's interest is in question reflects the unprincipled rhetoric of the current administration, alternately supporting and condemning regime change in North Africa, fighting extremism with strongly-worded tweets, putting political correctness before military readiness, and generally leaving both our friends and enemies confused as to where our priorities lie.

Our government has been infamously muddled in its handling of military spending and capabilities for many years. Public perceptions are drowned in buzzwords at the expense of accuracy: higher spending doesn't necessarily make us safer if it goes to useless projects, and "streamlining" doesn't necessarily mean more nimble, capable forces. With a new, energized Congress, there is a great opportunity to look at our military strength free from partisan politics and informed only by facts.

Progressive giant Teddy Roosevelt famously instructed, "Speak softly and carry a big stick." A century and many conflicts later, the White House seems to have forgotten his sage advice, losing its voice altogether and brandishing a stick that looks increasingly anemic and brittle.

Let us hope that it can be made whole again before we need to wield it, while praying that we never have to use it at the scale for which it should be prepared.

 - Jim DeMint is the president of The Heritage Foundation.