Expressions (phrases, clauses, etc.), Godan verb with 'tsu' ending
to hit someone where they least expect it; to take revenge on someone in an unlikely place; to get revenge on someone in a different contest; to attack the Edo enemy in Nagasaki
Idiomatic expression
Also written 江戸の仇を長崎で討つ【えどのかたきをながさきでうつ】