"Turn war into friendship" is a metaphor for turning war into peace or fighting into friendship. Jade and silk: Jade is jade, and silk is silk fabric. Both are the top quality for tribute, which is extended here to mean repairing things well and reciprocating courtesy.

Gange means weapons, and also refers to war or battle.

In the past, Gun, the leader of the Xia tribe, built a city three ren (eight feet is one ren) high to defend himself. Everyone wanted to leave him, and other tribes looked covetously at Xia. Later, when Yu became the leader, he discovered this situation and demolished the city walls, filled up the moat, distributed the property to everyone, destroyed the weapons, and taught the people morality. So everyone performed their duties, and other tribes were also willing to join. When Yu held a meeting of leaders in Tushan, tens of thousands of leaders came to present jade and silk treasures.

From "Huainanzi·Yuan Dao Xun": "In the past, Xia Gun built a city of three ren, and the princes turned against it, and there were cunning intentions overseas. Yu knew that the world was rebelling, so he destroyed the city and scattered the ponds. Treasures, armored soldiers, benevolence, foreign guests served, foreign ministers accepted, united the princes in Tushan, holding jade and silk to all nations."