Of the 73,661 servicemen listed as not recovered, as many as 8,597 were actually recovered decades ago or during the war. Unfortunately, lack of identification media and other factors compelled the military to inter them as unknown servicemen.
Each unknown received an X number, a unique identifier. In Europe the numbers related to the temporary cemetery at which the remains were interred. This system began during the war. The army established about sixty temporary cemeteries across northwest Europe and southern France. Some only saw short term use and soon closed, their burials transferred to other cemeteries. After the war, the AGRC inherited thirty-six temporary cemeteries in that area of Europe. The X numbers relate to those sites. Ten of them eventually became permanent cemeteries, and the unknown burials were distributed among them.
As for the X number system, the U.S. Army mortuary at Frankfurt, Germany, continued using it after the AGRC ceased operation. The mortuary eventually passed the progressive series of numbers to the present day U.S. Army Memorial Affairs Activity Europe.
For each X number, the army created a file containing all paperwork related to the case. This included burial reports, search-and-recovery narratives, and affidavits from civilians who had pertinent knowledge. The type and quantity of documents varied greatly from file to file. Today the X-files are stored at the Washington National Records Center but have not yet been accessioned to the National Archives.
The following X-Files are only related to the Netherlands:
X-File 3 came from Son Cemetery now-reburied at Margraten Cemetery.
X-File 5 came from Molenhoek Cemetery now-reburied at Margraten Cemetery.
X-File 15 Margraten Cemetery.
X-File 16 came from Molenhoek Cemetery now-reburied at Margraten Cemetery.
X-File 57 Margraten Cemetery.
X-File 58 Henri-Chapelle Cemetery
X-File 557 Henri-Chapelle Cemetery
X-File 786 Margraten Cemetery
X-File 1189 Margraten Cemetery
X-File 1194 Margraten Cemetery
X-File 1231 Margraten Cemetery
X-File 1265 Margraten Cemetery
X-File 1237 Margraten Cemetery
X-File `1991 Margraten Cemetery
X-File 1992 Margraten Cemetery
X-File 1993 Margraten Cemetery
X-File 1998 Margraten Cemetery
X-File 2004 Henri-Chapelle Cemetery
X-File 2015 Margraten Cemetery
X-File 2047 Margraten Cemetery
X-File 2055 Magraten Cemetery
X-File 2058 Henri-Chapelle Cemetery
X-File 2068 Margraten Cemetery
X-File 2140 Margraten Cemetery
X-File 2700 Margraten Cemetery
X-File 2799 Margraten Cemetery
X-File 3230 Ardennes Cemetery
X-File 3234 Henri-Chapelle Cemetery
X-File 3261 Ardennes Cemetery
X-File 3267 Ardennes Cemetery
X-File 3324 Ardennes Cemetery
X-File 3328 Ardennes Cemetery
X-File 3335 Ardennes Cemetery
X-File 3415 Ardennes Cemetery
X-File 3485 Ardennes Cemetery
X-File 4012 Ardennes Cemetery
X-File 4626 Ardennes Cemetery
X-File 4628 Ardennes Cemetery
X-File 4629 Ardennes Cemetery
X-File 4632 Ardennes Cemetery
X-File 4798 Ardennes Cemetery
X-File 5428 Ardennes Cemetery
X-File 5453 Ardennes Cemetery
X-File 5575 Ardennes Cemetery
X-File 6854 Ardennes Cemetery
X-File 7005 Ardennes Cemetery
X-File 7006 Ardennes Cemetery
X-File 7761 Ardennes Cemetery
X-File 7791 Saint-Avold Cemetery
X-File 7838 Ardennes Cemetery
X-File 8241 Normandy Cemetery
X-File 2881A Henri-Chapelle Cemetery
X-File 2118b Henri-Chapelle Cemetery