Short answers, pulled from the story.
Operation Weserübung was the Nazi German invasion of Denmark and Norway, which took place from the 9th of April to the 10th of June 1940. It opened the Norwegian Campaign of World War II and was one of the largest and most complex amphibious operations Germany conducted during the war.
Germany invaded Norway primarily to secure the supply of Swedish iron ore, roughly 90% of which was exported through the port of Narvik, and to establish naval bases for U-boat operations against Allied shipping in the North Atlantic. Grand-Admiral Erich Raeder had argued since October 1939 that Allied control of Norway would allow a blockade that would cripple German industry.
The invasion of Denmark lasted less than six hours on the 9th of April 1940, making it the shortest German military campaign of the war. King Christian X and the Danish government capitulated at approximately 06:00 after German forces seized airfields, bridges, and the Copenhagen harbour.
In the early morning of the 9th of April 1940, gunners at Oscarsborg Fortress fired on the advancing German fleet using two 48-year-old Krupp guns of 280 mm caliber, nicknamed Moses and Aron. The heavy cruiser Blucher was sunk within two hours with the loss of between 600 and 1,000 men, delaying the invasion long enough for the Norwegian Royal Family, Cabinet, Parliament, and national treasury to escape by train.
General Nikolaus von Falkenhorst was given command of the ground forces for Operation Weserübung on the 21st of February 1940. He had experience in Finland from the First World War and knowledge of Arctic warfare. He commanded the XXI Army Corps, which included the 3rd Mountain Division and five infantry divisions.
No. The International Military Tribunal rejected Germany's argument that the invasion of Norway was a justified preemptive strike against an imminent Allied attack. The tribunal found that German invasion planning dated to at least the 3rd of October 1939, and diary entries by Alfred Jodl from March 1940 showed Hitler was still searching for an excuse to launch the operation weeks before it began.