Is there a proverb that means something like an enemy's best tactic is to hide himself?
In 36 stratagems, there's one called Openly repair the gallery roads, but sneak through the passage of Chencang

(明修棧道,暗渡陳倉／明修栈道,暗渡陈仓, Míng xiū zhàn dào, àn dù chén cāng)

Deceive the enemy with an obvious approach that will take a very long time, while surprising him by taking a shortcut and sneak up to him. As the enemy concentrates on the decoy, he will miss you sneaking up to him.