It was the largest surrender of Federal forces during the Civil War.

Entity and relation annotations:
id: 0
type: entity
value: text: during the Civil War
labels: <Date>
id: 1
type: entity
value: text: the Civil War
labels: <Event>
id: 2
type: entity
value: text: Federal forces
labels: <Organization>
type: relation
to_id: 1
labels: Organization:Engagement:Event
from_id: 2