Dear Mr. Hanne,
Thank you for posting your request on History Hub!
Motion picture records of combat operations from the Army, Navy, Air Force, and Marines during World War I are in the custody of the National Archives at College Park - Motion Picture (RDSM). Please contact RDSM via email at firstname.lastname@example.org to see if any include the use of incendiary bombs, especially White Phosphorus, in the Pacific.
We hope this is helpful. Best of luck with your research!