Despite alliances with Britain and France who finally declared war on Germany on the 4th September – they did not mobilise on Poland’s Western Front.
The Polish Airforce was heavily outnumbered but fought brilliantly. From the Polish Navy 3 destroyers and two submarines escaped to Great Britain.
The Polish forces fought desperately but fell back on successive lines of defence. Warsaw was under siege. The Polish Commander-in-Chief Marshal Smigly-Rydz ordered the forces back to the south-east, towards Romania.
On 17th September 1939 the Soviets invaded Poland from the East and occupied the “Kresy” or “Eastern Borderlands”.
This was a result of the secret protocol of the Nazi-Soviet Non-Aggression Pact which agreed to divide Poland between them.
The Polish Army was retreating eastward and not yet re-grouped when faced with the Soviet invasion. The situation was chaotic.
Warsaw held out under siege from the Germans until 27th September. Sporadic fighting went on until the 5th October. Poland had fought alone for 6 weeks.