Synonyms for Commandeer:

n.

enlist, active service, activate, recruit, conscript, belligerent, battle cry, draft, bombed-out, Beleaguered, aggressor, air cover, active duty, enslave, black out. rob, sequester, requisition, repossess, go off with, encroach, seize. assume, preempt, arrogate. commandeer (noun)
hijack, pirate, highjack.

v.

contact (verb)
hijack, pirate, highjack.
seize, take over (verb)
grab, preempt, take, conscript, activate, confiscate, hijack, expropriate, assume, usurp, draft, requisition, enslave, sequester, annex, arrogate, appropriate.
take (verb)
confiscate, get, catch, capture, abduct, usurp, procure, take, gather, levy, impound, harvest, acquire, bag, annex, deprive, reap, monopolize, collect, appropriate, grab, nab, amass.

Other synonyms:

arrogate. preempt, seize, expropriate. assume. take
take.
take over
usurp.
Other relevant words:
enslave, assume, highjack, enlist, preempt, pirate, recruit, arrogate, requisition, seize, draft, activate, expropriate, sequester, conscript, hijack.