House Oversight Committee chairman Darrell Issa today issued a subpoena to secretary of state John Kerry, requesting that he turn over all documents and communications relating to the Benghazi talking points, including those belonging to Cheryl Mills, Hillary Clinton’s chief of staff at the time.

In a letter to Kerry, Issa said that the e-mails released by the White House in mid May did not indicate who at Foggy Botton aside from former State Department spokeswoman Victoria Nuland had expressed reservations about various aspects of the original talking points written by the intelligence community, “including language that made clear the State Department that had received prior warnings of threats in the region and was aware of previous attacks on foreign intersts in eastern Libya, and that extremists linked to al Qa’ida may have participated in the attacks.”

The State Department has thus far refused to turn over the documents voluntarily and, according to Issa, the materials are key to understanding why State Department leadership had reservations about acknowledging that extremists were involved in the attack that left four Americans dead.

Kerry has indicated his willingness to work with investigators and provide information on the attack, which occurred during the tenure of former secretary of state Hillary Clinton.

Issa’s letter to Kerry can be found here.