Honestly, they look like American police cars with that big "POLICE" word. When I first saw their photos, I even thought that they were photoshopped images. But they actually belong to crime scene unit or the forensic unit of the police through some quick searches.
The authorities blocked many roads in Hoàn Kiếm District to serve the celebrations. While there was initially a firework display, but it got canceled due to thd dreadful aftermath of the Yagi strom so there probably wouldn't be any military cars there.
Update: Well I have made my trip, there were a few police trucks around the area but all of them have been uploaded to the site. I have also came there late, since on the morning there were a lot of high ranking government officials like Prime Minister Phạm Minh Chính were there, so sorry about that. I also came across a fire drill with 2 fire engines, though there weren't many but it's better than nothing.
I actually have school on the morning and the afternoon, couldn't go out at noon due to the hot weather and I don't have enough time to do a trip there. Since I'm back to school, I could only spot vehicles at the weekend so it's a shame.