Question: Given the following passage  "In 1912, the Republic of China was established and Sun Yat-sen was inaugurated in Nanjing as the first Provisional President. But power in Beijing already had passed to Yuan Shikai, who had effective control of the Beiyang Army, the most powerful military force in China at the time. To prevent civil war and possible foreign intervention from undermining the infant republic, leaders agreed to Army's demand that China be united under a Beijing government. On March 10, in Beijing, Shikai was sworn in as the second Provisional President of the Republic of China.",  answer the following question. Note that the answer is present within the text.  Question: Who was the leader in the Republic of China who had the most power?
Answer:
Sun Yat-sen