History, however, is never tidy. Sir Michael Howard argues persuasively that Hitler’s onslaught in the west against France and Britain in 1940 was in many ways an extension of the First World War. Gerhard Weinberg also insists that the war which began with the invasion of Poland in 1939 was the start of Hitler’s drive for Lebensraum (living space) in the east, his key objective. This is indeed true, yet the revolutions and civil wars between 1917 and 1939 are bound to complicate the pattern. For example, the left has always believed passionately that the Spanish Civil War marked the beginning of the Second World War, while the right claims that it represented the opening round of a Third World War between Communism and ‘western civilization’. At the same time, western historians have usually overlooked the Sino-Japanese War from 1937 to 1945, and the way that it merged into the world war. Some Asian historians, on the other hand, argue that the Second World War began in 1931 with the Japanese invasion of Manchuria.
机翻：然而，历史从来都不是井井有条的。迈克尔·霍华德爵士有力地论证了1940年希特勒对法国和英国的西线进攻在许多方面是第一次世界大战的延续。格尔哈德·温伯格也坚持认为，始于1939年入侵波兰的战争是希特勒向东扩张 Lebensraum（生存空间）的开始，这是他的主要目标。这确实是真的，然而1917年至1939年间发生的革命和内战必然会使这一模式变得复杂。例如，左派一直坚信西班牙内战标志着第二次世界大战的开始，而右派则声称它代表了共产主义与“西方文明”之间第三次世界大战的第一回合。同时，西方历史学家通常忽视了1937年至1945年的中日战争，以及它如何融入世界大战。另一方面，一些亚洲历史学家则认为第二次世界大战始于1931年日本入侵满洲。
