Question

How did the Treaty of Tordesillas prevent war between Spain and Portugal?

Answer 1

The treaty prevented the war because The treaty moved the Line of Demarcation 800 miles further west. This gave Portugal more opportunity to claim lands unexplored by other Europeans.
While the portugals were exploring those land, the spain could obtain the resource from the conflicted territories without having to face the threat of the Portuguese's army.

Answer 2

Answer: The treaty prevented the war because The treaty moved the Line of Demarcation 800 miles further west. This gave Portugal more opportunity to claim lands unexplored by other Europeans.

While the portugals were exploring those land, the spain could obtain the resource from the conflicted territories without having to face the threat of the Portuguese's army.