lì / shǐ / kè / shàng / lǎo / shī / jiè / shào / le / Zhí / Wǎn / zhàn / zhēng / de / bèi / jǐng

历史课上，老师介绍了直皖战争的背景。

In history class, the teacher introduced the background of the Zhili–Anhui War.