A leak of this sort would vastly dwarf the cache of about 75,000 documents that WikiLeaks published in July from the Afghanistan War. That cache involved field reports from analysts who compiled information from informants and others on incidents and intelligence.

Overton said that his group is working on the new cache of documents with major television networks and print-media outlets in several countries, including the United States, to produce documentaries and stories based on them. The collaboration is similar to what was done in July when WikiLeaks worked with three news outlets — The New York Times, the Guardian and Der Spiegel — to simultaneously publish stories on the Afghan War logs.