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All's fair in love and war.
Literal
Romantic-love [and-と] battle [topic-は] means [object-を] do-not-choose.
A poetic variant of the 'love and war' proverb, with 戦 ('battle, fight') instead of 戦争. 戦 standalone is read いくさ (the native kun-reading), and this proverb is traditionally read 恋と戦(いくさ)は手段を選ばず. Proverb families repeated with slight wording variation are a normal trace of their oral-tradition origins.