Answer:
Tactical/Logistical incompetence and geography
Explanation:
The Soviet Union came into Afghanistan underestimating the Mujahideen. They believed they would be unorganized, awfully equipped, and tactically inferior. For the most part, they were right. The Soviet Union did have a stronger industry, better technology, more manpower, air superiority, and more equipment. However, they failed to recognize the logistical challenges of mountain warfare, and lacked the skill to fight in mountain warfare. The Afghani mountains are some of the largest and most unforgiving in the world. The steep angles and clouds of the mountains made it difficult for the Soviet Air Force to track and attack the enemy. In addition, trucks and supply lines were hard to get through, leaving many troops under equipped. The constant ambushes, low supplies, lack of air support, and Mujahideen guerrilla warfare in one of the most unforgiving environments on Earth eventually left the Soviet Union no choice but to withdraw their forces.
