In 1004, Liao forces managed to march deep into Song territory, camping out in Shanyuan, about north of the Song capital of Kaifeng. However, their forces were greatly overextended and any possible escape route was in danger of being blocked by Song forces. Eventually, the completion of the 'Great Ditch' as an effective defensive blockade which slowed the advance of Liao cavalry forced the Liao to request a truce. Negotiations resulted in the Treaty of Shanyuan, signed in January 1005 (some sources cite 1004 due to the Chinese Lunar Calendar), which fixed the borders of the Song and Liao as they were before the conflict. The Khitan rulers also wanted to intermarry with the Zhao family line of the Song, an offer that the Song refused in favor of a nominal and figurative imperial kinship. However, the treaty required the Song to make annual tribute payments to the Liao and recognize Liao equality with the Song. The tribute consisted of 283 kg (100,000 oz) of silver along with 200,000 bolts of silk, increasing to 500,000 units by 1042. However, even with the increase in 1042, the Song economy was not damaged by this enforced tribute. The bullion holding of the Liao dynasty did not increase with the tribute either, since the Song exported many goods annually to the Liao, dwarfing the amount of imported goods from Liao. Therefore, much of the silver sent to Liao as tribute was used to pay for Song Chinese goods, and the silver wound up back into the hands of Chinese merchants and the Song government.