Does "Til go back to Nanking if they'll sink their differences" mean "Until go back to Nanking, whether or not they will sink their differences"?
Context:
Personalities on the Chinese Scene 113
looking askance at Chiang Kai-shek's government. Later he
went to Nanking and was given a post, and then disgruntled
retired to the famous sacred mountain of T'ai Shan in Shantung
Province. Philip Fugh and I called on him once there. He was
reading an old classic and practicing his well-known calligraphy.
Til go back to Nanking if they'll sink their differences/' he said
emphatically. 'Til do anything, I'll take the highest position or
the humblest if they will only fight Japan/'
More:
http://www.archive.org/stream/fiftyyearsinchin012639mbp/fiftyyearsinchin012639mbp_djvu.txt