Pakistan carried out airstrikes on Afghanistan’s two largest cities on Friday, including the capital, Kabul, according to officials from both nations, escalating months of tension and border skirmishes into an open conflict. Beyond Kabul, home to six million people, the strikes hit the southern city of Kandahar — where the Taliban’s supreme leader, Sheikh Haibatullah Akhundzada, lives — and the border province of Paktia, according to Zabiullah Mujahid, a spokesman for the Taliban government. Pakistan launched the strikes hours after Afghan troops had attacked Pakistani border positions, according to Afghan and Pakistani officials. The Afghan attacks were described as retaliation...