Not a tl;dr, just my favourite bits:

Organizers believed that the fear induced by the event would help increase fundraising objectives.

The campaign was publicized in local newspapers for a few days before the event, although the "invasion" took many citizens by surprise.

Dressing stations were set up at strategic points to treat the mock casualties; they also treated the two real casualties of the event – a soldier who sprained his ankle, and a woman who cut her thumb preparing toast during the early-morning blackout.

The city was renamed "Himmlerstadt", and Main Street was termed "Hitlerstrasse".

At one local elementary school, the principal was arrested and replaced with a 'Nazi' educator dedicated to teaching the "Nazi Truth"; special lessons were prepared for high-school students throughout the city.

If Day was successful enough to spark imitations in other communities. The US government contacted the organizing committee for details of the event. A smaller-scale invasion was staged in Vancouver, using promotional materials from the Winnipeg campaign.