On this day in 1946 one of Berlin’s three plazas designed by Philipp Gerlach for Friedrich Wilhelm I (aka Soldatenkönig) - and because of its shape first called Rondell - had its name changed from Belle-Alliance-Platz to Franz-Mehring-Platz.
The plaza, once a real gem of urban und garden design, was located at the southernmost end of Friedrichstraße at Berlin’s southern city gate, Hallesches Tor. Several decades after Prussia paid Napoleon and his army back for invading it, humiliating its monarchs and stealing the Quadriga, many streets and squares south of the Landwehrkanal were named after important military leaders and victorious battles in Prussian Wars of Liberation. That’s when the Rondell became Belle-Alliance-Platz (Schlacht bei Belle-Alliance is what the Brits refer to as the Battle of Waterloo).

Practically swept off the face of the Earth in one of the worst WW2 air-raids on Berlin on February 3, 1945, and then damaged even further during the last (and completely futile) attempt at stopping the Red Army troops approaching from the south, the plaza survived in its name only. But not for long.
The idea came from the Department for Public Education of the Groß-Berlin Magistrat (it was before the separation of Greater-Berlin’s City Council into the western Senat and the eastern Magistrat). On February 13, 1946 - the 100th birthday of renowned Berlin Social-Democrat and journalist, Franz Mehring - they presented it on a larger forum and got the necessary support. It was the right moment, too: Berlin’s streets and plazas named after Nazis or Prussian militarists should be re-named to honour their opponents. And since Mehring, a Marxist publicist, wrote for the SPD newspaper the “Vorwärts” and the latter’s building was just around the corner in Lindenstraße (as if by miracle it survived the inferno, only to be demolished by West Berlin Senate), Franz-Mehring-Platz it was.

One and a half year later, on July 31, 1947, that name was shortened to Mehringplatz instead.