Tourists that visit the dike of the river IJssel near the village Olst are often amaze to see the turret of a Sherman Firefly along the road. In fact it is part of a large position, one of three of the IJssellinie. The turret defended the dike with its powerful 76,2 mm gun. It was restored a few years ago. This included the installation of a fake gun barrel, since the original gun had been removed.

After the Second World War the Netherlands was one of the few countries that still had confidence in permanent defenses. In 1953 the construction of the IJssellinie started. The three positions of the line each protection a dam. This could be closed with floating caissons. This way the river was blocked and the water level raised. Unlike in the other water lines there was a continous water supply, creating a stream in the inundations. This way it was impossible to cross with boats and amphibious vehicules.