Do you want to read the oldest classified documents in our collection? Learn how to make invisible ink? See the only classified documents still in existence from the first World War? Then you’re in luck.

Five years ago, the CIA declassified the US Government’s six oldest classified documents, dating from 1917 and 1918. These documents, which describe secret writing techniques and are housed at the National Archives, are believed to be the only remaining classified documents from the World War I era. Documents describing secret writing fall under the CIA’s purview to declassify.

“These documents remained classified for nearly a century until recent advancements in technology made it possible to release them,” former CIA Director Leon Panetta said during the document’s release 2011. “When historical information is no longer sensitive, we take seriously our responsibility to share it with the American people.”

One document outlines the chemicals and techniques necessary for developing certain types of secret writing ink and a method for opening sealed letters without detection. Another memorandum dated June 14, 1918 – written in French – reveals the formula the German’s used to produce invisible ink.

The documents are available on the CIA.gov eFOIA section and in the CIA Records Search Tool (CREST) at the National Archives in College Park, Maryland. CREST currently houses nearly 13 million pages of declassified Agency documents. Since 1995, the Agency has released over 36 million pages as a result of Executive Orders, the Freedom of Information Act (FOIA), the Privacy Act, and mandatory declassification reviews.

See the Secret Writing documents for yourself by clicking on the links below:

Secret writing document one (PDF 447 KB)

Secret writing document two (PDF 1.06 MB)

Secret writing document three (PDF 427 KB)

Secret writing document four (PDF 2.70 MB)

Secret writing document five (PDF 438 KB)

Secret writing document six (PDF 1.45 MB)