 Later that year, when Emperor Taizong was debating whether warring with Xueyantuo or making peace by marrying his daughter Princess Xinxing to Xueyantuo's Zhenzhu Khan Yi'nan, Fang was a proponent of peace, and Emperor Taizong agreed, although Emperor Taizong later changed his mind and broke the marriage treaty.In 643, when Emperor Taizong commissioned the Portraits at Lingyan Pavilion to commemorate the 24 great contributors to Tang rule, Fang's was one of the portraits commissioned.Later in 643, when Li Chengqian, fearing that Emperor Taizong would depose him in favor of his more favored brother Li Tai the Prince of Wei, was revealed to have plotted with Hou Junji to overthrow Emperor Taizong, Emperor Taizong had Zhangsun, Fang, Xiao Yu, Li Shiji, along with the responsible officials at the legislative and examination bureaus and the supreme court, investigate the matter.