Final answer:
Muhammad was both a political and religious leader because he unified political authority and religious leadership, which was manifested in the governance and expansion of the Islamic community. After his death, the caliphate continued this dual leadership tradition, intertwining politics with religion.
Step-by-step explanation:
Muhammad was not only the founder of Islam but also a political leader who had to steer his growing community through the challenges of establishing a new social order. In Medina, he successfully garnered followers and unified the religious and political dimensions of leadership, thereby becoming the indisputable leader of the Islamic community.
This dual aspect of his leadership is exemplified through various actions: his taking command in battles, like the fight against a Meccan army in 624, his strategic negotiation with enemies for the conquest of Mecca, as well as his expansionist endeavors that spread Islam across Arabia. His role extended beyond his death, as the question of his successor and the establishment of the title of Caliph continued to merge both religious authority and political power in leadership.
Following Muhammad's passing, the caliphate became an embodiment of this dual leadership, with the first Caliph being Abu Bakr, Muhammad's father-in-law. The caliphs after Muhammad maintained both the religious influence and political control, which were crucial in continuing the Muslim tradition and administering the Islamic territories.
This interconnectedness between trade, religious laws, and political structure underpinned the Islamic world, expanding its influence well beyond military conquest, and was pivotal for the sustained cohesion and expansion of the ummah or Islamic community.