Towing safety has improved dramatically in the last 75 years. Before the 1950s, the role of slowing down a trailer or towed vehicle fell on the towing vehicle until the Kelsey Hayes Company invented the first trailer brake controller (though early designs were mostly hydraulic as opposed to the electric designs we see on most modern towable RVs).
This is a companion discussion topic for the original entry at https://blog.campingworld.com/learn-to-rv/what-is-a-trailer-brake-controller-and-how-to-use-one/