I am not going to write it for you because that would be blatant plagiarism which against policy, but I can explain the entire subject of a topic enough to formulate an essay within your own ideas.
The topic will be the division of Korea after World War ll into the North and South.
There can be many underlying causes for the split of the Korean peninsula into North Korea and South Korea. Korean nationalists who resisted Japanese colonial rule mostly from abroad had divided into Communists and non-Communist groups much before 1945. Also you could argue that there were always cultural or political differences between the northern and southern regions due to their geographic and historical distinctions.
But the direct cause of the split obviously comes from the secret agreement made between the U.S. president Franklin Roosevelt and the Soviet premier Joseph Stalin at the Yalta Conference in February 1945. Roosevelt invited Stalin to declare war against Japan, despite the Soviet-Japanese non-aggression pact, and approved postwar Soviet control over Japan’s northern territories (Southern Sakhalin and the Kuril Islands) as well as harbors and railroads in Manchuria, present-day Northeast of China and Japan’s protectorate at the time.
It is not clear if the secret agreement mentioned Korea. But because the Soviets invaded and took over Manchuria so quickly, they naturally moved into northern Korea, just crossing the Manchuria-Korean borders. You see, the Soviets declared war against Japan on August 9th, exactly 3 months after German surrender, as Roosevelt and Stalin had agreed, attacking Manchuria and Japan’s northern territories. The Soviets forces simply swept through entire Manchuria just in several days and reached northern Korea by August 14th. By then, the U.S. realized what was happening, so it asked the Soviets to stop at the 38th parallel. Otherwise, the Soviets would have occupied the entire Korean peninsula. That’s how Korea north of the 38th parallel came under the Soviets and Korea south of the 38th parallel came under the U.S. The U.S. forces, coming from Okinawa, reached the peninsula only in September.
In my view, there was something seriously wrong with U.S. intelligence at this time. The U.S. apparently thought that the Soviets would be fighting the Japanese in Manchuria for months. But why? Didn’t Roosevelt and the top U.S. leaders know that the Japanese Kwangtung Army in Manchuria, once feared for its strength, was no longer there, because most of the troops had gone to fight the U.S. (and died) in the Pacific?
In sum, the U.S. ignorance (or disregard?) of Japan’s vulnerability in Manchuria and Korea in 1945 led to the Soviet invasion and occupation of Manchuria and Korea and ultimately the birth of a Communist state in northern Korea (as well as Chinese Communist advance via Manchuria).