1934 10 is about 25,000 kilometers, and the 18 mountain range spans 24 rivers. Why did the author only choose seven mountains and two rivers to write?

Because these seven mountains and two big rivers are the most difficult and typical ones to cross. As for the reflection of several mountains and rivers, it is only the artist's "artistic refinement". It won't cover everything.

Original text:

The red army is not afraid of the expedition, and Qianshan is just idle.

Wuling makes waves, and Wumeng takes mud pills.

Jinsha River is warm in the clouds and cliffs, and Dadu Bridge is cold with the cross rail.

I'm glad to see that Minshan Mountain is covered with snow and stretches for miles. Our soldiers crossed it and showed a bright smile.

Translation:

The Red Army is not afraid of all the difficulties and hardships on the Long March, and regards Qian Shan as ordinary. In the eyes of the red army, the continuous five mountains are just the ups and downs of microwave waves, and the majestic Wumeng Mountain is just a mud pill.

The Jinsha River is full of turbid waves, patting the towering cliffs and steaming. The cross frame of the dangerous bridge on the Dadu River is shaking the iron rope hanging high in the air, and the chill bursts.

What is more gratifying is that when we set foot on the snowy Minshan Mountain, everyone was smiling after the Red Army crossed it.

Extended data:

In just 56 words, "Seven Laws and the Long March" highly summarizes all kinds of difficulties and obstacles on the Long March. Through vivid and typical examples, he enthusiastically praised the revolutionary heroism and optimism of the heroic and tenacious Chinese Red Army of Workers and Peasants.

The Neck Couplet accepted "Ten Thousand Waters of Qian Shan", but the poet still chose two "Long March Maps": "Skillfully crossing Jinsha River" and "Forcibly crossing Dadu River". The rushing Jinsha River water beats the towering cliffs on both sides, and the mountains and rivers are singing for the victory of the Red Army. The Luding Bridge across the Dadu River has no wooden boards, but only 13 iron cables, which makes people look bleak. These two sentences describe the Red Army's conquest of water.

The poet did not describe the battle of Jinsha River positively. The situation at that time was very critical under the pursuit of powerful enemy forces. The Red Army only used seven ships. Nine days later, Kuya sneaked across the Jinsha River, annihilated the enemy on the other side and broke through the encirclement.

The poet wrote the cold river so warm, which is the joy of victory revealed by the poet on the river bank after the victory of the battle. The other water is the Dadu River. The Red Army captured the Luding Bridge in cold weather. The iron cable of Luding Bridge hangs high above the rushing river, and the cold light is shining, which reminds people of the tragic scene of the Dadu River Campaign.

The contrast between "warm" and "cold" is strong, which is not only an objective fact, but also a poet's psychological feeling. It not only expresses the joy of the Red Army after crossing the Jinsha River, but also shows the hardships and tragic battles of crossing the Dadu River and flying over Luding Bridge, which is soul-stirring and shows the bravery of the Red Army.