It's simply a matter of perspective for the author. Hugh Deane was a journalist during the 1940's and 50's he saw the political games of the cold War as the causes of the Korean War. Which is ofcourse true. By this he means that the US asked for control and administration of southern Korea while the USSR would do the same in the north. The US government was actually quite surprised when the USSR agreed to these terms as it really didn't have to. The USSR had take that entire swathe of land from the Japanese in the last days of WW2 and had defacto control over it as in Eastern European countries. The Author postulates that the Korean War, (which he believes should be characterized as a civil war) started there and then in 1945 the moment the Americans split the country and the newly minted UN allowed it. It is however a mischaractirazation of the war to say the north did not invade the south first. The author simply puts into context that the violence in the country between communist and anti communist started years before the actual start of hostilities in 1950. The North Koreans did invade the south in 1950 when there was no official state of war between the two koreas. The US and later UN did come in to rescue the South Korean regime from being toppled by the north that is all true. The author simply states it is equally true that if the US hadn't tried to play politics immediately after ww2 that the division of Korea and the war as a whole would never have happened.