A mass grave of troops from the second Battle of Himera in Sicily in 409 B.C. One-fourth of the combatants are thought to have been mercenaries, compared to two-thirds in the first Battle of Himera seven decades earlier. Stefano Vassallo

Wherever there is an out-of-the-way war, there will be mercenaries — hired fighters whose only common bond may be a hunger for adventure. Some join foreign armies or rebel forces because they believe in the cause; others sign on because the price is right...

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