The kingdoms of Kapisa-Gandhara in modern-day Afghanistan, Zabulistan and Sindh (which then held Makran) in modern-day Pakistan, all of which were culturally and politically part of India since ancient times, were known as "The Frontier of Al Hind". The first clash between a ruler of an Indian kingdom and the Arabs took place in 643 AD, when Arab forces defeated Rutbil, King of Zabulistan in Sistan. Arabs led by Suhail b. Abdi and Hakam al Taghilbi defeated an Indian army in the Battle of Rasil in 644 AD at the Indian Ocean sea coast, then reached the Indus River. Caliph Umar ibn Al-Khattab denied them permission to cross the river or operate on Indian soil and the Arabs returned home.