Context: On February 1842, during the First Opium War, Prince Yijing, cousin of Emperor Daoguang and the Commander of the offensive against British occupation in eastern Zhejiang, went to a temple in Hangzhou and asked for a fortune stick (kau chim). On the stick it said some riddles about "tigers" (不遇虎头人一唤，全家谁敢保平安).
In Chinese, people use the word "Yang Ren (洋人)" to represent foreigners. The word "洋" (Yang) means something foreign or related to the ocean, but also has the same pronunciation and similar structure of the word "羊" (sheep).
Inspired by the fortune stick and the Tibetan reinforcements that wore tiger hides in battles, Yijing had a genius idea that he can use "Tigers" to eat the "Yang (sheep)" for breakfast. Therefore, he came up with the strategy called "Five tigers ambush the Yang (五虎扑洋之计)".
The battle plan is as follows:
The timing is very important. According to traditional Chinese beliefs, he chose the time to commence the counteroffensive on year 1842 (Year of the tiger), March (Month of the tiger) the 10th (Day of the tiger), at 4 in the morning according to Chinese calendar (Hour of the tiger). For the commander, he hand picked Duan Yongfu, a general who was born in the Year of the tiger. Therefore all five "tigers" are set for the plan. In the opening phase, the Tibetan soldiers who wore tiger hides would be the assault force to eat up the force of "yang" by force of surprise.
I guess this is about the battle of Ningpo (there is no mention of tigers on the Wikipedia article)
https://en.wikipedia.org/wiki/Battle_of_Ningpo