Ok, it's from Wikipedia, but I couldn't find a better source:
http://en.wikipedia.org/wiki/Yuan_Chonghuan#Later_military_career_and_death
"In 1628, under a new government, Yuan Chonghuan was reinstated as field marshal of all the forces of the northeast. He embarked on an ambitious five year plan for the complete recovery of Liaodong. In 1629 he was granted the title of Senior Guardian of the Heir Apparent. The
Chongzhen Emperor, the new emperor gave him his Imperial Sword and stated that he would fully support Yuan's decisions.
This time Yuan had to face again a larger Manchurian force (slightly above 200,000) under Huang Taiji. This time the Manchurians had incorporated many more men including the newly surrendered Mongols, rebel Ming army and the conquered Korea and various small states of the North. However, the Manchus were not confident to attack Jinzhou or Ningyuan again.
The Manchus changed their strategy. They bypassed Jinzhou, Ningyuan and Shanhai Pass. They broke through the Great Hall west of Shanhai Pass and suddenly appeared north of Beijing in the winter of 1629. Yuan rushed back with an elite army from Ningyuan to defend the capital. He reached Beijing only one or two days before the Manchus arrived at Beijing. Outside the city wall of Beijing, he defeated the Manchurian "
Eight Banners" (八旗) which numbered one hundred thousand."
So, WI he had arrived later, or had died before reach the city, and the Manchu had been able to invade the city? Would it be the end of the Ming dynasty 15 years earlier? And what kind of consequences could it bring?