On 29 April 1904, Hazrat Mirza Ghulam Ahmad received the Word from God 'Korea is in a dangerous situation. Eastern power.' The footnote to the annotated edition of the collection of his revelations records a slightly different word-order:
When the war started between Japan and Russia, and Japan had not yet achieved any significant victory, the Promised Messiah received this revelation: 'An Eastern power and Korea's delicate situation.' Many members of our Jamaat [Community], especially those who live in Qadian, know about this revelation. I regret that I failed to publish this earlier. I am recording it now because I feel that this new Eastern power has a special relevance to the Ahmadiyyah Jama‘at. (Allah knows best.)Note by Maulana Abdul Latif Bahawalpuri: Before the war between Russia and Japan, Korea was under the control of the Russia. This war was concluded with a peace treaty on May 27–28, 1905. The first clause in the treaty was that Japan will have complete sovereignty over Korea. Thus with the victory of the Eastern power (Japan) and the defeat of Korea, this prophecy of the Promised Messiah was clearly fulfilled. It should be noted that the prophecies have multiple fulfillments. Now that the East is gaining greater prominence on the international scene, it seems that the future events will unfold a new commentary of this revelation, [As Allah the Almighty so wills]. 
The second Caliph of the Ahmadiyya Muslim Community writes about this as one of the prophetic miracles of a political nature shown to Ghulam Ahmad (the founder of the Community) and states that he received this revelation as the The Russo–Japanese War began:
As is evident from the words of this revelation it was vouchsafed therein that Japan would be the victor in this war and that it would receive such a glorious victory that it will be able to fulfill its wish of capturing Korea. But the Koreans will not like this and a dangerous chaos and insurrection will take place which will destroy the country. Although at the time this revelation was published even the greatest of political statesmen and those in government could not have uttered such a thing and some people were not even willing to accept that Japan will emerge victorious let alone entertain such a hope and thought that Russia is still ignorant of the impact this war. They thought that in time it will use its endless resources to crush Japan and nobody would have imagined that if Japan won they will have to fulfill its demands but see how the events of the future unfolded to prove the truth of this Word? Japan won and Russia fell victim to such diabolical rioting that it had to make peace and succumb to Japan's demands and accept its power over Korea but the Korean hated this greatly and seeing Japan's insistence it raised the flag of revolt against it and this country remained in a state of danger for many many years thereafter and the way the peace there has been disturbed cries at the top of its voice in approval of its delicate state that was revealed to His Holiness the Promised Messiah. 
Another essay he wrote in December 1951 on the subject of Communism & Democracy is also worth reading in this context.
The fifth Caliph mentioned this prophecy in his Friday Sermon of 9 May 2003 and said that the situation in Korea is unstable to date.
 Ahmad, Hazrat Mirza Ghulam. Tadhkirah. Second English Edition. ( Islam International Publications Ltd, 2009). 667, 668.
 Ahmad, Hazrat al-Hajj Mirza Bashirudeen Mahmood - Khalifatul Masih II. Tohfa Shehzada Wales [Gift to the Prince of Wales]. 1922. In Anwarul Uloom: vi. (Fadl-I-‘Umar Foundation). 520, 521.