all come as a shock;be difficult to guard against (/to prevent); be impossible to defend effectively; cannot reckon with all eventualities; indefensible; there is no stopping
❍ 家门不幸，真是～！ (茅盾《子夜》240) This house is disgraced! It’s all come as such a shock!/这种小人，真是～。(吴趼人《二十年目睹之怪现状》372) It was difficult to guard against those cunning men.
❍ 现在又要添上个电话，作为我和外界的第三道桥梁，岂不更使他们～？ (爱新觉罗·溥仪《我的前半生》139) A third link with the outside in the form of a telephone would put them in an impossible position.
防不胜防fánɡ bù shènɡ fánɡ
比喻防备不过来。be difficult or impossible to prevent(ward off), very hard to guard against, can’t reckon with all eventualities, impossible to guard against