Is the word enemy plural or singular?
Yes, you can use enemy with a plural verb, but when you do so it is only ever as a collective or mass noun, never as a countable one. The paywalled OED has this as its sense 3a: a. The hostile force.
What is the plural form of enemy?
noun. en·e·my | / ˈe-nə-mē / plural enemies.
Is enemy a collective noun?
Obviously in this case enemy is a collective noun. This usage is much more common in British English than in American English, and doubly so when reading literature of less recent authorship. English is not a clearly defined language. Theres a lot of ambiguity, especially in the more advanced rules.