The type of decision that increases a nation's sphere of influence is called a (n) policy.

The type of decision that increases a nation's sphere of influence is called an Expansionist policy. This is a form of an aggressive and radical nationalism where expansionism is the main goal. Expansion in terms of military and economic context that caused a lot of major conflicts and colonization in history.

answer; the tempest"s caliban,may be your answer; /// good luck