The Beast

The film is prefaced with a quotation from the poem "The Young British Soldier" by Rudyard Kipling:
When you're wounded an' left on Afghanistan's plains
An' the women come out to cut up your remains
Jus' roll to your rifle an' blow out your brains
An' go to your Gawd like a soldier.
In 1981 Afghanistan, a Soviet tank unit viciously attacks a Pashtun village harboring a group of mujahideen fighters. Following the assault, one of the tanks, commanded by the ruthless Commander Daskal (George Dzundza), gets separated from the unit and enters a blind valley. Taj (Steven Bauer) returns to discover the village destroyed, his father killed and his brother martyred by being crushed under the tank, to serve as execution for disabling and killing a Russian tank crew. As the new khan, following his brother's death, Taj is spurred to seek revenge by his cousin, the opportunistic scavenger Mustafa - and together they lead a band of mujahideen fighters into the valley to pursue the separated tank, counting on their captured RPG-7 anti-tank weapon to destroy it.
The tank's crew is made up of four Soviets and an Afghan communist soldier. As night falls and the crew sets up camp, the Afghan tank crewman Samad (Erick Avari) educates the tank driver, Konstantin Koverchenko (Jason Patric), about the fundamental principles of Pashtunwali, the Pashtun people's code of honour: milmastia (hospitality), badal (revenge), and nanawatai, which requires even an enemy to be given sanctuary if he asks. As the plot progresses, Commander Daskal (called "Tank Boy" during World War II for destroying a number of German tanks when he was a child soldier during the Battle of Stalingrad) demonstrates his ruthlessness not only to the enemy, but also to his own men. He despises Samad for his ethnic association to the enemy and, after a couple of attempts to kill him, finally gets his wish on the pretext of suspecting Samad of collaborating with the mujahadeen. After Koverchenko threatens to report Daskal for the killing, Daskal entraps him and orders Kaminski (Don Harvey) and Golikov (Stephen Baldwin) to tie him to a rock, with a grenade behind his head to serve as booby-trap for the mujahideen. Some wild dogs come upon him and as Koverchenko tries to kick at them, the grenade rolls down the rock and explodes, killing several dogs but leaving Konstantin unhurt. A group of women from the village, who had been trailing the mujahideen to offer their support, come across Koverchenko and begin to stone him, calling for his blood as revenge (badal). As the mujahideen approach, Koverchenko recalls the term nanawatai (sanctuary) and repeats it until Taj cuts him free, and allows him to follow their procession. That night, hidden in a cave, the fighters eat and Taj asks Koverchenko in broken language if he will fix their non-functioning RPG-7, and help them destroy the tank.
As the remaining three members of the tank crew begin to realize they are trapped in the valley, a Soviet helicopter appears and offers to rescue them. Daskal, caring more for his tank than his men, refuses the offer and simply refills the vehicle's oil and gasoline. They get their bearings from the helicopter pilot and head back into the narrow mountain pass from which they came, looking for the way out of the valley. Ironically, they later return to a water hole (which they earlier poisoned with cyanide to try and kill the mujahideen) to cool the engines, and find the helicopter crew dead, having drunk from the small pool. The mujahideen and Koverchenko catch up with the tank crew there, and a cat-and-mouse chase begins near the mountain pass, culminating in an opportunity for Koverchenko to disable the tank with the RPG. Konstantin fires as the tank is going out of range, but damages only the main gun. Just as it seems the tank will escape, an explosion set off by the village women (who are equipped with grenades) in the cliffs above the tank sets boulders rolling onto it, disabling it at last. The tank crew is forced out and Koverchenko pleads nanawatai on their behalf. Taj reluctantly agrees. Konstantin tells Daskal that he wants him to live to see the Soviets lose the war, which is "no Stalingrad", and states that "It's hard to be a good soldier in a rotten warâ¦ how is it that we're the Nazis this time?" Kaminski and Golikov flee on foot presumably to safety, but Daskal is overrun by the women, who carry out their vengeance by stoning him before taking his bloodied uniform and boots as trophies and being reprimanded by Taj for their barbaric and merciless act.
A Soviet search-and-rescue helicopter appears, and despite the camaraderie that has developed between him and Taj, Konstantin goes with the helicopter. Taj orders his men not to fire on him as he is being hoisted up into the helicopter. Before being hoisted up by the helicopter's rescue winch, Koverchenko salutes Taj by brandishing an Afghan jezail musket, which Taj gave to him earlier, above his head. The film ends with Koverchenko being hoisted up to the airborne helicopter, flying away, the jezail still clenched in his hand.

Question: What was done to the water hole?
Answer: poisoned