Before the late 1930s Hitler didn’t really care too much about Poland and the Poles, apart from the odd comment. The main Germans who were against the Poles were the Prussians rather than the Austrians. The latter were mostly hostile towards Czechs.
As an Austrian, his main anti-Slav antipathies were directed at the Czechs, not the Poles.
Ian Kershaw,
Hitler 1936-1945: Nemesis.
Consequently, in the 1920s, Germany's attitude vis-à-vis Poland was predominantly hostile. In view of this widespread anti-Polish sentiment it is surprising that Poland barely surfaced in Mein Kampf. There, Hitler did not exploit or even refer to these obvious anti-Polish sentiments. Hitler, in fact, did not comment on Germany's past and present relations with Poland or about its future relations under a National Socialist government. If Mein Kampf tells us anything at all about Poland, it is that Hitler rated the 'racial value' of the Poles as low - though without going into any detail.
Apart from this rather brief comment, Hitler mentioned Poland only in the context of his opposition to an alliance with Russia. According to Hitler's conclusion, accurate in the context of the Polish-Russian antagonism of the early 1920s and the Polish-French alliance, 'Russia would first have to subdue Poland' before it could join Germany in a war with 'Western Europe'. Only from Hitler's very curt assessment that Poland was 'completely in French hands' can it be assumed that he had little time for Germany's eastern neighbour.
Hitler's 1928 manuscript offers a slightly better insight into his views on Poland and the Poles. Again, he refers to the lower 'racial value' of the Poles - this time, however, in more detail and in stronger language. Again he deemed Poland a major obstacle in a potential Russian military move westward. More clearly in fact than in Mein Kampf Hitler concluded that 'a subjugation of Poland by Russia . . . is quite improbable' while he also discussed, in more detail, Poland's role as an ally of France and thus as a very likely enemy of Germany. In contrast to Mein Kampf, the Secret Book refers explicitly, though with surprising brevity, to the fate of those Silesians, East and West Prussians 'enslaved under Polish rule'. In attacking anti-Italian 'agitators' in Germany, Hitler reminded them that other nations, including Poland, had also committed crimes against the Germans.
By and large, however, Poland played only a marginal role in Hitler's major writings. What stands out from Mein Kampf and the Secret Book is Hitler's disapproval of the Polish 'race' and his agreement with the powerful anti-Polish and revisionist sentiment in Germany. Other sources of the 1920s reveal a similar attitude ('Poland was created from German blood') though again Hitler mentioned Poland only infrequently.
Christian Leitz,
Nazi Foreign Policy, 1933-1941: The Road to Global War, pages 63-64.
He was not, himself, violently anti-Polish; he was an Austrian, and the Catholic Austrians traditionally regarded Poles with some favour.
Norman Stone,
Hitler.
Hitler, as an Austrian, had never been anti—Polish as such, unlike the general mood in the Reich, especially so in the Auswärtiges Amt (the German Foreign Office).
Panikos Panayi,
Weimar and Nazi Germany: Continuities and Discontinuities, page 159.
Perhaps Hitler would have concentrated less on Austria and Czechoslovakia if he had not been born a subject of the Habsburg Monarchy; perhaps his Austrian origin made him less hostile originally to the Poles.
A. J. P. Taylor,
The Origins of the Second World War, page 28.