Not only did he fail to break up the fight — he egged it on.
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history
From Wang Tong's 《文中子·问易篇》 (Sui): 真君建德之事,足推波助澜 — acts attributed to Emperor Zhenjun 'push the waves and aid the billows'. The original sense leaned neutral; modern usage is almost always negative.
usage
Predominantly negative now — worsening an already-bad situation (rumors, conflict, panic). Compare with 火上浇油 (pour oil on fire), which is more vivid and physical.