Why was Germany so successful from 1939-1942?

From 1939-1942, Germany was extremely successful on the battlefield. In 3 years, they reclaimed the Rhineland and also took Poland, Denmark, Norway, and large portions of Russia. The German army was so successful because of Blitzkrieg and Hitler’s nationalism. Blitzkrieg was a very successful battle tactic used by Germany during World War II. Blitzkrieg means "lightening war," which is exactly what Hitler wanted to have as it would use less resources and less men would die, keeping Hitler's army strong. Blitzkrieg would start with the Luftwaffe which would bomb a point on the enemy line. The German tanks would then break through the enemy lines. The tanks and infantry caused distracting chaos behind the initial enemy line and would then turn back to encircle, or surround, the enemy. This battle tactic lead to German success because it took advantage of the weaponry, tanks, bombers, and artillery, effectively. Hitler's nationalism to his country allowed Germany to be widely successful. When Hitler came to power, people were excited for change. Hitler quickly improved economy and re-militarized, giving many people jobs. He also united the country by eliminating all political parties other than the Nazi party. People quickly put trust into him as he had done so much to improve Germany. The uniting and rebuilding of the economy gave Hitler the support of the entire country which enabled Hitler the countries permission to go to war. Hitler's Germany, in 1942, only began declining because his ingenious battle techniques were used against him.