Short answers, pulled from the story.
The Second Vienna Award was a 1940 territorial settlement between Romania and Hungary that transferred Northern Transylvania to Hungarian control. The treaty was signed on the 30th of August 1940, by Foreign Ministers István Csáky of Hungary and Mihail Manoilescu of Romania.
The 1930 Romanian census registered 2,393,300 inhabitants while the 1941 Hungarian census recorded 2,578,100 residents. Discrepancies existed because Hungarian statistics listed 1,380,500 Hungarians whereas Romanian figures showed only 912,500 Hungarians in the region.
Hungarian troops committed massacres including the Treznea massacre on the 9th of September 1940, and the Nușfalău massacre on the 8th of September 1940. Lieutenant Zoltán Vasváry commanded forces responsible for killing villagers in Ip on September 13 and 14, 1940.
Romania built the Carol II fortified line between 1938 and 1940 to defend its western border with Hungary but the entire line fell within the area allotted to Hungary. The Hungarian Army salvaged metal and equipment before blowing up the casemates to prevent their reuse by Romania.
The Allied Commission voided the Second Vienna Award through the Armistice Agreement with Romania on the 12th of September 1944. The 1947 Paris Peace Treaties reaffirmed the borders as originally defined in the Treaty of Trianon 27 years earlier.