Final answer:
The friendly tribe attacked by Bacon and his men during the period of rising tensions in Virginia was the Susquehannock, which led up to Bacon's Rebellion.
Step-by-step explanation:
The tribe attacked by Bacon and his men during tensions between English colonists and Native American tribes in Virginia was the Susquehannock, who were friendly towards the colonists. Nathaniel Bacon and his followers initiated offensive actions against the Susquehannock without the proper commission from Governor William Berkeley, amidst broader conflicts and disputes about the colony's Indian policy and territorial expansion. This led to the outbreak of Bacon's Rebellion, where Bacon's forces attacked not just the Susquehannock but also other tribes in the area, such as the Doeg, which greatly impacted the region and the relationships between the colonists and various Native American groups.