Most of us take it on faith that our military is the best in the world. But if asked to state in detail how ready we are to face certain challenges from around the globe, few of us would know how to answer.

How prepared is each branch — Army, Navy, Air Force and Marines — to handle its missions? What is our nuclear capability? What are the threats we face in Asia, the Middle East and Europe, and how could we respond to them?

You might think that policymakers in Washington are on top of that, and sure — there are attempts to measure our state of readiness.

Our intelligence community produces threat assessments of specific countries and the world as a whole. The Department of Defense produces its Quadrennial Defense Review report at the start of each presidential term. The president issues the national security strategy report required by law. The military services conduct their own studies.

This is in addition to various congressional commissions and innumerable other studies that come from think tanks and other interested groups. So there is no shortage of reports. What’s missing is a consistent and comprehensive annual review of the state of our national defense, what we may be called on to do, and how ready we are to do it.

Until now. The 2015 Index of U.S. Military Strength, featuring insights and analysis from the nation’s top defense analysts, is designed to fill that gap.

The need for the index should be obvious. You can’t get from Point A to Point B without knowing how you’re going to get there. Without a realistic inventory of what your transportation options are, you can’t make the best decision about how to travel.

For that matter, you can’t decide where you’re going to go in the first place without knowing why. That’s what the Index of U.S. Military Strength is meant to do: give not only the how, but also the why. It’s not enough to know that it’s a dangerous world. We need to know the who, the where and the when.

You may know, for example, that the Middle East is a global hot spot, but do you know the state of Iran’s ballistic missile threat? Its longest-range missile can reach as far west as Egypt and Ukraine, and as far east as China and India. Iranians are working to expand that range at a furious pace. According to the Pentagon:

“Iran could develop and test an ICBM capable of reaching the United States by 2015. Since 2008, Iran has conducted multiple successful launches of the two-stage Safir space launch vehicle and has also revealed the larger two-stage Simorgh space launch vehicle, which could serve as a test bed for developing ICBM technologies.”

In Asia, we have North Korea (among others) rattling the saber. It has an extensive ballistic missile force, with about 800 Scud short-range tactical ballistic missiles, 300 No-dong medium-range missiles and 50 Musudan intermediate-range ballistic missiles. This isn’t bad news for South Korea alone, but also Japan and U.S. bases on Okinawa and Guam.

Not every threat comes from a missile silo, however. The index assesses, among other things, the growing problem of cyberterrorism — which nations are capable of what kind of attack. The 2009 theft of F-35 plans from the Department of Defense? Courtesy of China. The 2012 data theft by “Energetic Bear” that targeted the international energy sector, manufacturers and defense contractors? Russia was responsible. And so on.

There aren’t many specific tasks that the U.S. Constitution assigns to the federal government, but national defense is one of them. To “provide for the common defense” in the most sensible, cost-effective and successful way possible, we need to know what tools we have, what their state is and how we may need to use them.

That is where the 2015 Index of U.S. Military Strength comes in. Let’s hope policymakers put it to good use.

 - Ed Feulner is founder of The Heritage Foundation