(CBS) 60 Minutes asked the Department of Defense to grant us an interview. They declined. Instead, they sent a letter, which contains a figure not included in published casualty reports: "More than 15,000 troops with so-called 'non-battle' injuries and diseases have been evacuated from Iraq." Many of those evacuated are brought to Landstuhl in Germany. Most cases are not life-threatening. In fact, some are not serious at all. But only 20 percent return to their units in Iraq. Among the 80 percent who don’t return are GIs who suffered crushing bone fractures; scores of spinal injuries; heart problems by the hundreds; and a slew of psychiatric cases. None of these are included in the casualty count, leaving the true human cost of the war something of a mystery. "It's difficult to estimate what the total number is," says John Pike, director of a research group called GlobalSecurity.org. As a military analyst, Pike has spoken out against both Republican and Democratic administrations. He’s weighed all the available casualty data and has made an informed estimate that goes well beyond what the Pentagon has released. "You have to say that the total number of casualties due to wounds, injury, disease would have to be somewhere in the ballpark of over 20, maybe 30,000," says Pike.