刀山火海 dāoshān-huǒhǎi
[seas of fire and a forest of knifes-an extremely dangerous place which is most difficult to get through] 比喻极困难和极危险的地方,也说“火海刀山”
峻青 《黎明的河边》一:“为了拯救河东区正在遭受着敌人蹂躏的老百姓,前面就是刀山火海,我也决不退缩。”