Ukrainian soldiers carry cartridges in their position on the frontline, near Bakhmut, Donetsk region, Ukraine, Friday, April 7, 2023. AP
The documents, which were posted on sites such as Twitter, are labeled secret and resemble routine updates that the U.S. military's Joint Staff would produce daily but not distribute publicly.
The New York Times was the first to report about the documents. Later Friday, the Times reported that more documents involving Ukraine as well as other sensitive national security topics such as China and the Middle East had begun appearing on social media.
Analysts believe that over 100 documents may have been accessed due to the breach.
They are dated ranging from Feb. 23 to March 1, and provide what appears to be details on the progress of weapons and equipment going into Ukraine with more precise timelines and amounts than the U.S. generally provides publicly.
They are not war plans and they provide no details on any planned Ukraine offensive. And some inaccuracies — including estimates of Russian troops deaths that are significantly lower than numbers publicly stated by U.S. officials — have led some to question the documents' authenticity.
Experts have struggled to reach judgments about who disclosed the material and why. Some believe the disclosure attempts to foment discord between Washington and Kyiv.
The US Justice Department has launched an investigation, which comes as questions continued to swirl about the origination and the validity of the documents, and as reports suggest more have begun to appear on social media sites.
Officials at the Pentagon acknowledge that the duplicates are genuine Defense Department documents, although they appear to have been altered in several ways from their original format.
While determining the source of the leak is challenging, the episode is part of a pattern of more document breaches in the Ukraine war.