TIL- In ww1 planes forward firing gun was synchronized with the propeller to fire through the propeller

https://www.uh.edu/engines/epi1369.htm#:~:text=They%20put%20metal%20deflectors%20on,Enter%20now%20Holland's%20Anthony%20Fokker.

https://www.reddit.com/r/todayilearned/comments/151w3my/til_in_ww1_planes_forward_firing_gun_was/