This is the end of the world. This is the day you're going to die.

Sources:
We've Got Hostiles (remix), by morch kovalski:    • Black Mesa  We've Got Hostiles (remix)  
Afghanistan Helmet Cam Combat:    • Afghanistan Helmet Cam Combat  Heavy...  
Left Behind In A Firefight In Afghanistan:    • LEFT BEHIND IN A FIREFIGHT IN AFGHANI...  
Intense сity battle ambient:    • Intense сity battle (ambient sounds) ...  
War Radio Chatter:    • War Sounds  Radio Chatter  1 Hour  
Black Hawk Down:    • Black Hawk Down: Get Us Off This Stre...  
Saving Private Ryan:    • Saving Private Ryan 4K UHD  Omaha Be...  
Call For Backup:    • Call For Backup  Veterans You Are No...  
DShK Heavy Machine Gun Shooting:    • Ukrainian Soldiers Fire Giant Super S...  
More DShK shooting:    • Shooting a DShK Heavy Machine Gun  
And even more DShK:    • DShK belt fed machinegun at Knob Creek  
HECU Radio Chatter Sounds:    • HECU Radio Chatter Sounds [Black Mesa]