sentences:  The collapse of Mohammad Najibullah's regime in April 1992 led to a peace treaty between the Afghan political parties.But soon after, the undisciplined commanders from both former mujahideen and Communist ranks started to vie for power, abetted by foreign powers, namely Pakistan, Saudi Arabia, Iran, and Uzbekistan, who began arming their Afghan proxies to fight for control and influence.With the breakup of the Soviet Union in 1991, the Soviet-supported government of Najibullah lost credibility.