[1][3]: 39, 42  On 1 September 1939 the Invasion of Poland was initiated by Germany when the battleship Schleswig-Holstein opened fire on the Polish-controlled harbor of Danzig, around 04:45–48 hours.

Danzig paramilitaries and police, supported by Germany, immediately joined the offensive to take full control of the city, by capturing the Polish post office.

All but four of the defenders, who were able to escape from the building during the surrender, were sentenced to death by a German court martial as illegal combatants on 5 October 1939, and executed (the judgement was later acknowledged as judicial murder).

As tensions between Poland and Germany grew, in April 1939 the Polish High Command detached combat engineer and Army Reserve Sublieutenant (or 2LT) Konrad Guderski (1900–1939) to the Baltic Sea coast.

With Alfons Flisykowski and others, he helped organise the official and volunteer security staff at the Polish Post Office in Danzig, and prepared them for possible hostilities.

The Polish employees had a cache of weapons, consisting of three Browning wz.1928 light machine guns, 40 other firearms and three chests of hand grenades.

[4] The Polish defence plan assigned the defenders the role of keeping Germans from the main building for six hours, when a relief force from Armia Pomorze was supposed to secure the area.

At 04:45, just as the German battleship Schleswig-Holstein started shelling the nearby Polish Army military outpost at Westerplatte, the Danzig police began their assault on the building under the command of Polizeioberst Willi Bethke.

Mortar support was requested from the German forces at Westerplatte, but its inaccurate fire posed a greater threat to the attackers and it soon ceased action.

At 17:00, the bomb was set off, collapsing part of the wall, and German forces under the cover of three artillery pieces attacked again, this time capturing most of the building except the basement.

[11] The prisoners were mostly executed by firing squad led by SS-Sturmbannführer Max Pauly (later commandant of the Neuengamme concentration camp) on 5 October and buried in a mass grave at the cemetery of Danzig-Saspe (Zaspa).

A similar fate awaited eleven Polish railway workers from Tczew south of the city, who were executed by the SA after they foiled a German attempt to use an armoured train in a sneak attack.

[14] Schenk stresses the commanding role of Danzig police forces, which made a Wehrmacht court martial not competent to convict the defenders.

In the chapter, the protagonist Oskar Matzerath meets his presumptive father Jan Bronski as the latter heads home, trying to avoid fighting in the looming battle.

[18] In 2012 the Polish rock/metal band Horytnica [pl] has written a song titled "Obrońca Poczty w Gdańsku" ("Defender of the Post Office in Danzig").