Which poem did Zhu De write about the Red Army joining forces with Jinggangshan?

Revolutionary heroes will get through and concentrate on becoming stronger. After the improvement of the leadership of the Red Army, the five broken sieges consolidated the battlefield.

1July, 957, Zhu De recalled the scene of joining forces with Jinggangshan, and wrote this song "Joining forces with Jinggangshan" with passion. This poem is magnificent, although it is a few words, but it outlines a magnificent picture of the revolutionary struggle in full swing after Zhu Mao joined forces with Jinggangshan and Zhu Mao joined forces with Jinggangshan. There is a profound historical background between the lines.