The Institute for the Study of War and Strategy hosts conferences on a regular basis.
Afghanistan: Lessons Learned, with Gen. David Petraeus (Februay 11-13, 2019)
Past conferences include:
Military Innovation (December 3-4, 2018)
The British Home Fron 1914-1918 (June 20-22, 2018)
The Present and Future of Air Power (May 8-9, 2018)