After the war, in the 1950s, butter became the smugglers' object of choice to traffic [from the Netherlands] to Belgium. [...]
[The] battle between the smugglers and the government customs officers intensified. The size of the shipments increased and so did the financial risks. There was no shortage of firearms available, and criminals were not afraid to use them against pursuers. They also used trucks and cars fitted with armoured plating to break roadblocks.
Opportunities for smuggling came to an abrupt end when Belgium, the Netherlands and Luxembourg formed a customs union, which became effective in 1962.
A contemporary account from The Tuscaloosa News has the following to add about the methods of the Dutch butter smugglers:
They use tradesmen’s vans with disguised armor-plating to dodge bullets, old but powerful American cars, motorcycle combinations, boats, or just human lift and carry.
When pursued they have been known to throw spikes or home-made bombs on the road in front of customs’ cars. Another device is to lay a smoke-screen by trickling salad oil from a pipe inside the car into the tail end of the hot exhaust pipe.
Sources:
- Antonopoulos, Georgios: Illegal Entrepreneurship, Organized Crime and Social Control (2016) p.61f
- The Tuscaloosa News, 21st December 1962
@Boukert