Everything is Ready Except the East Wind

China has been divided into three kingdoms historically: Wei in the north, Shu in the southwest and Wu in the southeast.

Once Cao Cao from Wei led a 200,000 strong army down to the south to wipe out the kingdoms of Wu and Shu. Therefore, Wu and Shu united to defend his attack. Cao ordered his men to link up the boats by iron chains to form a bridge for the Cao's passing from the north bank of Yangtze River to the south bank. The General Commander of the allied army was Zhou Yu. He analyzed the situation carefully. Then he got a good idea. He decided to attack the enemy with fire. So he began to prepare for the coming battle. Suddenly he thought of the direction of wind. He needed the east wind to blow strongly in order to accomplish his scheme. However, the wind did not come for days. Thus Zhou Yu was worried about it. At that time, he got a note from Zhuge Liang, the military adviser of the State of Shu, which reads:
"To fight Cao Cao, Fire will help you win.
Everything is ready, Except the east wind"

Quickly he turned to Zhuge Liang for help. Zhuge told him not to worry and there would be an east wind in a couple of days. Two days later, the east wind helped Zhou accomplish his scheme. At last, the allied army won the war.

Later, people use it to say "All is ready except what is crucial".

萬事俱備 只欠東風

歷史上，中國曾被分為三大國：北邊是魏國，西南是蜀國，東南是吳國。

有一次，魏國的曹操帶了二十萬精兵南下攻打吳國和蜀國，準備消滅它們。為了應敵，吳國和蜀國結成同盟國。曹軍駐紮在長江北岸。曹操讓手下用鐵鏈將戰船連在一起，好讓曹軍渡江攻打南岸的盟軍。盟軍由吳國將領周瑜帶領，他仔細分析了形勢，最後決定用火燒掉敵人的船。於是，他開始準備一切，當他將一切準備好時，發現還需要東風。可連續幾天都沒有東風，周瑜急得病倒了。這時，蜀國的軍師諸葛亮叫人送了一張紙條給他，上面寫著：「要贏曹操，須用火攻。萬事俱備，只欠東風。」周瑜收到後，立刻向諸葛亮求助。諸葛亮叫周瑜不要著急，兩天後，將有東風。果然，兩天後，刮起東風。周瑜趁這個機會將曹軍的戰船燒燬，最後，曹操被打敗了。

後來，人們用這個成語來比喻樣樣都準備好了，只差最後一個重要條件。