Answer:
Yes it's correct. The entire group was surrounded by enemy forces.
Step-by-step explanation:
grammatically in this case group is classified as singular. Was surrounded should be correct.
When you are talking about every member of the group, it is singular.
However when you are talking about fractions of the group, it is plural. For example Except for the snipers, the group were surrounded by enemy forces on all sides. Not easily understood, but that's the way English works.