2 sentences for 役 (yì — battle)

1. 我们要努力拼搏，毕全功于一役。

   wǒ​men yào nǔ​lì pīn​bó, bì quán gōng yú yī yì.

   We must strive hard to finish the whole task in one fell swoop.

   Source: Dong Chinese Dictionary

2. 这一役打得非常艰难，双方都损失惨重。

   zhè yī yì dǎ de fēi​cháng jiān​nán, shuāng​fāng dōu sǔn​shī cǎn​zhòng.

   This battle was hard-fought, and both sides suffered heavy losses.

   Source: Dong Chinese Dictionary