In the movie Брестская Крепость imdb.com/title/tt1343703/ about the first days of German attack on Brest Fortress, a Soviet soldier is shown tying 3 grenades together while being attacked by German tanks with infantry. I have no military training. Is it realistic? It seems like the grenades won’t hurt the tanks, and 3 separately thrown grenades may inflict more damage upon infantry than one large (heavy, and potentially misplaced) explosion.
I believe the idea behind bundling them together was to increase the size of the explosion to be able to knock off a track and disable the tank. In those days there wasn’t a lot that that the infantry man would have at his disposal to attack a tank with unless he had some anti-tank weapons.
Theoretically there is a better chance of doing damage with several grenades at once… although I have never tried it myself :)
I beleive the Germans did a similar thing where they modified the “potato masher” grenade by adding extra grenade heads around the central body. Would probably be a large enough explosion to disable the track on a tank or do a number on a bunker. Not sure if this was an official design or a field expedient one…
As far as I know these were to be used against the top of the engine compartment which was a rather weak spot those days. In the early days of the war these might have shown some effect.