Eight-character idioms in the Three Kingdoms

Everything is ready except the east wind.

Commentary: Everything is ready, except for the east wind, which can't make a fire. Everything is ready, except for the last important condition.

From: Ming Luo Guan Zhong's Romance of the Three Kingdoms, Chapter 49: "Kongming takes a pen and paper, and the screen retreats left and right. The secret book is sixteen words: if you want to break Cao Gong, attack him with fire; Everything is ready, only the east wind. "

Ex.: We can install the machine as soon as it comes.

Grammar: complex sentences; Make provisions; Wait for an opportunity