(literary) friend or foe?; Which side are you on?; specifically whether one belongs to the Nationalist side (led by 蒋介石 jiǎng​jiè​shí) or the collaborationist side (led by 汪精卫 wāng​jīng​wèi) during the War of Resistance. Originally a quote from the opera 沙家浜 shā​jiā​bāng.