My colleague, Sara Lee, has a post on the successful test of the Ground-based Midcourse Defense (BMD) portion of the ballistic missile defense program.

This is just to give you a bit of background on the test, what it means, and what it doesn’t.

This system is designed to work in concert with other components of the ballistic missile defense system by targeting ICBM’s outside the atmosphere in the late stage of acceleration, at the apogee, and immediately prior to reentry. It is a kinetic energy weapon that relies upon metal-on-metal impact rather than explosives.

The test: A simulated ICBM was launched from Kwajalein Atoll and the interceptor was fired from Vandenburg AFB in California.

The BMD program has been rife with critics since its inception. They’ve largely been proven wrong at every step along the way but let’s look at some of the critiques. This from a staffer at the Union of Concerned Scientists:

Even if the test is successful, it is very important to look holistically at the capabilities of the system and what has actually been demonstrated. While this test may demonstrate that the Missile Defense Agency is on the right track with the fixes to the kill vehicle, overall it is not even close to demonstrating that the system works in a real-world setting. The system has not yet been tested in the range of conditions under which it is expected to operate—for example, it hasn’t been successfully tested at night or against complex countermeasures that a determined adversary would surely try to include. The Pentagon’s Director for Operational Test and Evaluation assessment in 2014 is that the tests to date are “insufficient to demonstrate that an operationally useful defense capability exists.”

A successful test this week is the basis for better understanding the capabilities of the system, but it is not the basis for expanding the system. Whether this week’s test is successful or not, the GMD system is still far from being able to provide reliable protection from a real-world missile threat.

Not tested at night? Because radar doesn’t work in the dark? Because the ground crew would be asleep?

There are some valid points here but they are couched in an “It won’t work but if it does work it doesn’t mean anything” rhetorical broadside. Realistically, the GMD would be of marginal use against a full on assault by Russia or China. Both those nations (I’m less familiar with China’s arsenal than Russia’s) have MIRV and maneuverable warheads. This means that unless the GMD hit the ICBM before tip over, it would be overwhelmed by the MIRVed warheads and decoys. But Russia and China really aren’t the threats. The threats are North Korea and Iran. Neither of those nations have missiles that are any more sophisticated than the test parameters we saw this week.

And yes, even North Korea’s limited number of ICBMs would probably achieve some successes IF we stood by and let them shoot until they got tired. That, however, is not going to happen. The storage and known launch sites are going to be subject to very intense airstrikes. ICBM’s can’t do a cold launch and achieve anything like accuracy. We were able to target SCUDs in Iraq by looking for tell-tale signal signatures. We would do the same in the case of Korea.

And this:

On Tuesday, Philip Coyle, a senior fellow at the Center for Arms Control and Non-Proliferation, told CNN the test “marks two successes in a row, which is significant,” but added that only two of the last five attempts were successful. “In school, 40 percent isn’t a passing grade,” Coyle told the news outlet. “Based on its testing record, we cannot rely upon this missile defense program to protect the United States from a North Korean long-range missile.”

Two in a row is actually more significant than saying two of the last five because it signals that certain basic engineering problems have been solved. Even did the 40% number hold true, this is overcome by multiple engagements per target. While it is true that we can’t rely upon this system right now, that doesn’t mean we can’t rely upon it in the future and the GMD is simply part of a larger toolbox. A goalie can’t stop every shot but you’d be an idiot to not use a goalie.

The overall mission of the GMD and the other BMD components is to increase the level of uncertainty for North Korea and Iran to deal with. If you can’t guarantee your missiles can hit targets, do you really want to launch them? Because unless they can cause mass casualties and force a quick end to hostilities neither of those nations lasts more than a couple of weeks under the full weight of the US military. In particular, this was a message to North Korea that we will not be blackmailed into accepting a North Korean weapon. We will make progress faster on the GMD than North Korea will make on MIRVs, decoys, or maneuverable warheads. That knowledge is certainly going to factor into their decision-making.