Most of the papers are marked "official sensitive", a relatively low level of classification used, according to the government, "where there is a clear and justifiable requirement to reinforce the 'need to know'".
But one document, addressed to Ben Wallace's private secretary, and marked "Secret UK Eyes Only", outlines highly sensitive recommendations for the UK's military footprint in Afghanistan, following the end of Operation Resolute Support, the Nato operation currently winding down in the wake of President Biden's decision earlier this year to withdraw American forces.
The document discusses an American request for British assistance in several specific areas, and addresses the question of whether any British special forces will remain in Afghanistan once the withdrawal is complete.
Media reports have already suggested Britain is considering leaving some forces behind.
Due to the sensitivity of the document, the BBC has decided not to report details which could endanger the security of British and other personnel in Afghanistan.
But amid reports of a worsening security situation in the country, it sounds several warnings.
"Any UK footprint in Afghanistan that persists... is assessed to be vulnerable to targeting by a complex network of actors," it says, noting that "the option to withdraw completely remains."
Afghanistan, it says, is already becoming more dangerous.
The reduced presence of Nato forces "is already impairing the situational awareness that we (and the US) used to enjoy across the country".
No Britons have been killed in Afghanistan since the US-Taliban deal in February 2020, it says, but "this would be unlikely to remain the status quo".