The annual Cobra Gold military exercise began in Thailand on Tuesday.
The event sees thousands of US troops taking part in a series of grueling and garish tasks all in the name of survival.
Twenty-nine other nations are also attending the largest event of its kind in the Asia-Pacific region, which teaches troops how to survive in extreme conditions in the jungle.
Around 4,500 members of the US armed forces will be taking part in drills on land and sea. Alongside them will be there counterparts from Singapore, China , Japan , India, South Korea, Indonesia and Malaysia.
The training is now in its 39th year and lasts for 10 days.
The US Marines got stuck into the drills on Tuesday as they lined up to drink the blood of a decapitated cobra – which is said to be a good source at re-hydrating the body should drinking water not be available during a jungle mission.
Some of the pictures show the bright red blood being dripped onto their tongues.