Rambo: First Blood Part II

A year into his sentence, former commando John Rambo (Sylvester Stallone) is visited by his old commander, Colonel Sam Trautman (Richard Crenna). With the war in Vietnam over, the public has become increasingly concerned over news that a small group of US POWs have been left in enemy custody. To placate their demands for action, the US government has authorized a solo infiltration mission to confirm the reports. As one of only three men suited for such work, Rambo agrees to undertake the operation in exchange for a pardon. He is taken to meet Marshall Murdock (Charles Napier), a bureaucratic government official overseeing the operation. Rambo is temporarily reinstated into the US army and instructed that he is only to photograph a possible camp and not to rescue any prisoners or engage enemy personnel, as they will be retrieved by a better equipped extraction team upon his return.
During his insertion, Rambo's parachute becomes tangled and breaks, causing him to lose most of his equipment, leaving him with only his knife and a bow with specialized arrows. He meets his assigned contact, a young intelligence agent named Co-Bao (Julia Nickson), who arranges for a local, river pirate band to take them upriver. Reaching the camp, Rambo spots one of the prisoners tied to a cross shaped post, left to suffer from exposure, and rescues him against orders. During escape, they are discovered by Vietnamese troops and attacked. When a gunboat manages to catch up, the pirates betray them out of fear. Rambo gets the POW and Co-Bao to safety, destroys the boat with an RPG-7, and kills the pirates. When Rambo calls for extraction, the helicopter is ordered to abort by Murdock, who claims Rambo has violated his orders.
Co-Bao escapes, but Rambo and the POW are recaptured and returned to the camp. There, Rambo learns that Soviet troops are arming and training the Vietnamese. He is turned over to the local liaison, Lieutenant Colonel Podovsky (Steven Berkoff) and his right-hand man, Sergeant Yushin, for interrogation. Upon learning of Rambo's mission from intercepted missives, Podovsky demands that Rambo broadcast a message disavowing the POWs. Meanwhile, Co infiltrates the camp disguised as a prostitute and comes to the hut in which Rambo is held captive. Rambo at first refuses to cooperate, but relents when the prisoners' lives are threatened. Instead of reading the scripted comments, Rambo directly threatens Murdock. He then subdues the Russians with Co's help and escapes into the jungle. They kiss, and Rambo agrees to take Co back to the United States. However, a small Vietnamese force attacks them, and Co is killed. An enraged Rambo kills the soldiers and buries Co's body in the mud.
Using his weapons and guerrilla training, Rambo systematically dispatches the numerous Soviet and Vietnamese soldiers sent after him. After barely surviving a barrel bomb dropped by Yushin's helicopter, Rambo climbs on board, throws Yushin over the side in a brief fight, and takes control. He lays waste to the prison camp and kills all of the remaining enemy forces before extracting the POWs and heading towards friendly territory in Thailand. Podovsky, pursuing in a Mil Mi-24 helicopter gunship,[7] shoots them down and moves in for the kill. Having faked the crash, Rambo kills him with a spare rocket.
Returning to base with the POWs, Rambo, after using the helicopter's machine gun to destroy Murdock's office, confronts the terrified man with his knife demanding that Murdock rescue the remaining POWs. Trautman then confronts Rambo and tries to pacify him. An angry Rambo responds that he only wants his country to love its soldiers as much as its soldiers love it. The film credits roll as Rambo walks off into the distance while his mentor watches him.

Question: Who learns that Soviet troops are arming and training the Vietnamese?
Answer: Rambo