Stumbled over this Sherman marked with the green circle/triangle of the Aggressor Forces, circa 1951. It's a Tennessee Army National Guard vehicle.
(https://i.imgur.com/xsla0Hi.png)(https://i.imgur.com/LRt9HbG.png)
(The 1959 FM p.61 - below - says those markings are supposed to be 36" diameter on the front slope, 20" on each side and 45" for the air recognition on the back deck.
(https://i.imgur.com/t3ON3ks.jpg)(https://i.imgur.com/fVpslMa.jpg)
Got curious, vaguely remember reading about this Cold War fabrication and started digging - so enjoy!
Here's the 1959 Field Manual bad link https://www.alternatewars.com/WW3/Trigons/FM30_101_1959.pdf (https://www.alternatewars.com/WW3/Trigons/FM30_101_1959.pdf)
link updated 29FEB24 https://www.bits.de/NRANEU/others/amd-us-archive/Fm30-101%2861%29.pdf (https://www.bits.de/NRANEU/others/amd-us-archive/Fm30-101%2861%29.pdf)
and the 1962 update https://archive.org/details/FM30-101/page/n149/mode/2up (https://archive.org/details/FM30-101/page/n149/mode/2up)
The 1966 Order of Battle ( FM 30-103) has the elaborate backstory.
http://www.bits.de/NRANEU/others/amd-us-archive/FM30-103%281966%29.pdf (http://www.bits.de/NRANEU/others/amd-us-archive/FM30-103%281966%29.pdf)
Their language? Esperanto!
Awesominto, si!?
(https://i.imgur.com/xz4xCX8.jpg)
Aaaaaaaaaaaaaand here's your one stop shopping page
https://www.alternatewars.com/WW3/Trigons/Trigons.htm (https://www.alternatewars.com/WW3/Trigons/Trigons.htm)
This guy can barely keep a straight face in his outfit.
(https://64.media.tumblr.com/54f7c0ac35d54a824cb1a7dc6946167b/tumblr_nw3u3xPuFt1sqx1wto1_1280.jpg)
Enjoy a transmission of truth and facts
https://www.youtube.com/watch?v=jBk14NLKUKs (https://www.youtube.com/watch?v=jBk14NLKUKs)
Be a good excuse to repurpose all those late-war Panzers.
American 105mm Recoilless Rifle crew engaging a Trigon Panther tank at close range.
(https://i.imgur.com/YHItY8l.jpeg)