Vietnamese bikes are strong, one speed, wide tire workhorses.
I remember my former co-worker, a disabled vet from the Vietnam war, once telling me a story about finding a cache of bicycles used by the Vietcong to transport weapons and supplies. As the story goes, they tried using hand grenades to destroy the bikes with little success. Finally, they had to get a tank to run over them to destroy the bikes.
Ken Whittaker