In 1939 Polish State Railways had 220 thousand employees. It was a well-organised occupational group. 85% of railwaymen were members of trade unions. Most of them were also members of the Railway Military Training Organisation who had done compulsory military service. As part of mobilisation activities, some railwaymen were summoned to join the army. In the last weeks before the outbreak of war numerous cases of German sabotage against railway facilities were recorded. Some acts of sabotage were prevented thanks to vigilant railway workers. The most tragic act of terror was an explosion of a time bomb on 28 August at 11:18 PM in the waiting room of the railway station in Tarnów. The lethal device was planted by Antoni Guz from Bielsko. 20 people were killed under the ruins of the destroyed railway station and 35 were injured.
The first military transports were put into operation before mobilisation was declared; 5 large troops were transferred at that time. Subsequent echelons were transported under a mobilisation plan which provided that 32 out of 56 large troops would be transported by rail, as a whole or in part, to build-up points. In total they were to account for 3/5 of Polish forces. This task required 3 thousand trains. In addition, railways had an obligation to deliver 700 thousand reservists from emergency mobilisation and 400 thousand from general mobilisation and 100 thousand soldiers withdrawn from the west to reserve centres situated in the east. Railway troops were supposed to remove damages to railroads.
The attack of Nazi Germany on Poland on 1 September 1939 was also aimed at main junction stations and railway lines. Bombing raids on the stations in Tczew and Kutno started at dawn. Also, the bridge on the Bugonarew in Modlin was bombed. To prevent the progress of the German army, Polish sappers blew up some railway structures e.g. viaducts, tunnels in Żegiestów (on the line Muszyna – state border) and in Łupków (on the Łupków – Medzilaborce line), bridges in Tczew, Grudziądz, Bydgoszcz-Fordon, on the Bydgoszcz Canal, in Toruń and in Płock.
When war broke out railways were handling emergency and general mobilisation transports. Also, the first evacuation trains pulled out on the route. Germans carried out bombing raids and airborne fire attacks on railway stations, echelons but also on evacuation trains carrying civilians and identification-bearing sanitary trains. Large railway stations such as those in Bydgoszcz, Grudziądz, Inowrocław, Toruń, Łowicz, Piotrków Trybunalski, Skierniewice, Kraków, Lublin and the stations of the Warsaw railway junction were bombed – some of them even more than once. Despite this fact, railwaymen and sappers were able to restore traffic on the damaged lines within 3 – 4 hours.
The events in Szymankowo became a symbol of the heroism of rail-waymen. Here, Polish railwaymen prevented an insidious seizure of the bridge in Tczew by the Germans. The scheduled transit train was followed by an armoured train which was sent to a sidetrack and derailed. In retaliation Germans murdered the railwaymen from Szymankowo. In Chojnice, instead of the scheduled train, a German armoured draisine pulled into the station followed by an armoured train. Polish railwaymen and soldiers had been able to take control of the draisine and destroy the bridge before the armoured train reached it. Two railway companies took part in the defence of Warsaw.
Armoured trains were used in the defensive war, including “Danuta” (No. 11) and “Poznańczyk” (No. 12) which took part in the Battle of the Bzura and were destroyed. “Generał Sosnkowski” (No. 13) was derailed and damaged after a bombing raid near Łochów. “Paderewski” (No. 14) was destroyed near Łowicz, and “Śmierć” (No. 15) suffered damage during fighting near Modlin. “Pierwszy Marszałek” (No. 51) fought both against Germans and the Red Army and was damaged in combat with Soviet airplanes. “Piłsudczyk” (No. 52), “Śmiały” (No. 53) and “Bartosz Głowacki” (No. 55) were seized by the Soviets in Lviv (Podzamcze), and “Groźny” (No. 54), fighting in Silesia, was destroyed by the crew when they reached a blown-up bridge on the Dunajec.
As a result of the warfare, 11 large bridges were destroyed, 8,000 smaller structures were damaged and 25,000 damages to stations and tracks were recorded. Some trains and evacuated rolling stock – the exact number is difficult to estimate – reached the eastern parts of the Republic of Poland that on 17 September were occupied by the Red Army.