strike the iron while it is hot; try the blade while it is sharp; go into battle while the morale of the troops is high/……養(yǎng)精蓄銳，以待～。(魯迅《兩地書》五) …We should conserve strength and store up energy,and wait for the opportunity to strike while we are at our best.
及鋒而試ji feng er shi
wield the sword when it is sharp—take action when there is an advantage
及鋒而試jí fēnɡ ér shì
及：趁、當(dāng)；鋒：鋒利。趁著鋒利的時(shí)候試用。比喻抓住有利時(shí)機(jī)，及時(shí)行動(dòng)。strike the iron while is hot, go into bettle while the morale of the troops is high, come up to the tip of a bayonet and try