The Afghan Taliban’s success in mediating between militants and the government in neighboring Pakistan could help bolster the credibility of the transitional government in Kabul and assuage some regional security concerns by showcasing the Taliban leaders’ ability to prevent cross-border terrorism. A month-long cease-fire deal between Tehreek-e-Taliban Pakistan (TTP), also known as the Pakistani Taliban, and the government of Pakistani Prime Minister Imran Khan went into effect on Nov. 9. The deal, which was facilitated by the Afghan Taliban, calls for Pakistan to release some TTP soldiers in exchange for pausing attacks until Dec. 8, which have escalated in the wake of the Taliban’s success in Afghanistan over the summer....