How to Cite an IGO Document in Chicago style
A report is referenced in the following format in Chicago style


  Last name, First name. Title of Work. Publisher city: Publisher, Year
  of publication. Accessed Month Date, Year. URL.


In the case of your report you have 2 authors and an unknown place of publishing so Bibliographical note would be;


  Cullen, Dr. Patrick J., and Erik Reichborn-Kjennerud. MCDC Countering
  Hybrid Warfare Project: Understanding Hybrid Warfare. N.p:
  Multinational Capability Development Campaign (MCDC), 2017. Accessed
  September 26, 2018.
  https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/647776/dar_mcdc_hybrid_warfare.pdf.


As you can see N.p is used to show that there is no record of place of publisher. This can be seen in this guide and this question.

Your first footnote should look like this;


  Dr. Patrick J. Cullen and Erik Reichborn-Kjennerud, MCDC Countering Hybrid Warfare Project: Understanding Hybrid Warfare (N.p:
  Multinational Capability Development Campaign (MCDC), 2017), page number.


Your subsequent footnote should look like this;


  Cullen, MCDC Countering Hybrid Warfare Project: Understanding Hybrid Warfare, page number.