What was a main power source for a longship sail or oars?

The main power source for a longship was its sails, which harnessed wind to propel the vessel across the water. In addition to sails, longships were also equipped with oars, allowing them to maneuver effectively in shallow waters or during calms when wind was insufficient. This combination of sail and oar made longships versatile and capable of swift travel across various marine environments.