Which poem in the poem makes the frontier war tight and heavily guarded?

The answer is that the desert is lonely and straight, and the long river sets the yen.

Riding a bike to visit the border and passing through Juyan County.

Pengpeng also floated out of Korea, and the geese heading north also flew into the sky.

The vast desert is lonely, and the Yellow River sets the yen.

When I arrived at the small pass, I met a spy waiting for the knight and told me that Dou Hu was in Yan.

From the mission to the front,

Passing through Juyan country on the way.

Like grass floating outside Hans,

Like a goose flying home, it flew into the sky.

Smoke rises straight in the desert,

The setting sun is round just beside the Yellow River.

Walking to Xiaoguan coincides with waiting for the bus.

Duhu is in the front line of Yanran.