The 'Battle of Hel' was fought between German and Polish forces on the Hel peninsula of Poland’s Baltic Sea coast within the context of the 'Weiss' (i) German invasion of Poland (1 September/2 October 1939).

The defence of the Hel peninsula took place around the Hel Fortified Area, a system of Polish fortifications constructed in the 1930s near the interwar border with the German Third Reich.

Beginning on 20 September 1939, after the Armia 'Pomorze' had been defeated in the 'Battle of the Tuchola Forest' and after other Polish coastal strongholds had capitulated in the 'Battle of Westerplatte', 'Battle of Gdynia' and 'Battle of Kępa Oksywska', Hel was the only substantial pocket of Polish military resistance left in northern Poland. It was also the site of the invasion’s only naval surface engagement.

The Germans blockaded the defenders of the Hel peninsula from the start of the war and launched no major land operations until the end of September. Some 2,800 Polish soldiers under Kontradmirał Włodzimierz Steyer, part of the Land Coastal Defence formation, defended the Hel Fortified Area for about 32 days, until they surrendered for lack of supplies and a collapse of morale.

Construction of a Polish navy port at Hel, on the tip of the Hel peninsula, began in 1931, and in 1936 the northern section of the Hel peninsula was officially declared the Hel Fortified Area. Work on the fortifications had not been completed before the outbreak of war, but over several months, as tensions between Poland and Germany had mounted, the fortifications had been reinforced with provisional earthworks.

The Hel Fortified Area had coastal and anti-aircraft artillery batteries. The Coastal Artillery Division’s coastal batteries comprised one of four 152-mm (6-in) guns, two of two 105-mm (4.13-in) guns and three of eight 75-mm (2.95-in) guns. The 2^nd Naval Anti-aircraft Artillery Division’s batteries were equipped with six 75-mm (2.95-in) and eight 40-mm guns, seventeen machine guns and two 120-cm (47-in) searchlights. Infantry cover for the Hel Fortified Area was provided by the Hel Border Defence Corps Battalion under the command of Major Jan Wiśniewski, and this battalion had several pieces of artillery (four of 75-mm/2.95-in and six of 37-mm calibre), 62 machine guns, and two large and nine small mortars. The Coastal Artillery Division had 162 men, the 2^nd Naval Anti-Aircraft Artillery Division 1,000 men and the Border Defence Corps Battalion 1,197 men.

Overall command was exercised by Steyer, but Hel also became the headquarters of the Polish navy’s commander, Kontr­admirał Józef Unrug, who relocated his command centre there on the eve of the invasion on 31 August, concluding that the Hel Fortified Area was better suited to prolonged defence than the more provisional defences around his peacetime headquarters in Gdynia. Unrug also reinforced the Hel garrison with soldiers from his Gdynia garrison.

In September, therefore, some 2,800 men were stationed in the Hel Fortified Area. While the Hel coastal batteries were the most powerful in Poland, they were nonetheless inadequate to confront warships of the German navy and posed no great threat all all to any of the German capital ships. Likewise, the Polish air-defense batteries in the region were too few and too light to deter German aircraft, and the Polish warplanes tasked with defending the area and stationed at the nearby town of Puck, were both older than their German counterparts and outnumbered by about 20/1.

Hel was attacked by the Luftwaffe from the first day of the invasion, starting at 13.30 on 1 September. This initial attack targeted the Polish coastal batteries. The second air raid, at 18.00 on the same day, targeted ships in the port, damaging the Polish light minelayer Mewa. Further air raids occurred during the course of the following day. On 3 September, the Polish destroyer Wicher and large minelayer Gryf, supported by Polish coastal-battery fire, engaged two German destroyers Leberecht Maass and Wolfgang Zenker in what was the only naval surface engagement of 'Weiss' (i), and was relatively inconsequential. Leberecht Maass sustained light damage and four fatalities, while Gryf also sustained light damage, with seven fatalities. The German ships retreated, and later that day the Luftwaffe sank Gryf, Wicher and Mewa. The gunboat General Haller sustained heavy damage, was abandoned, and sank on 6 September. Another Polish gunboat, Komendant Piłsudski, though largely undamaged, was also abandoned. This effectively eliminated the already heavily outnumbered surface Polish navy as a fighting force in the Baltic Sea, and from this time onward Poland had only several light units operational in the theatre. The surviving crews of the sunken Polish vessels joined the garrison’s defenders, and two 120-mm (4.72-in) guns from Gryf were salvaged for shore-battery use.

In the first week of September, General Günther von Kluge’s 4^th Army of Generaloberst Fedor von Bock’s Heeresgruppe 'A' forced the Armia 'Pomorze' to retreat from the Danzig 'corridor', took Puck, and on 9 September began to assault the Polish forces on the Hel peninsula. The advancing German forces included the 42^nd Grenzwachtabschnitt and the 5^th Kavallerieregiment. The Polish defenders began a slow retreat toward the port of Hel at the south-eastern tip of the peninsula. On 10 September the Germans captured the village of Swarzewo, and on 11 September the town of Władysławowo near the base of the peninsula. The Polish defenders fortified the next village, Chałupy, about one-fifth of the way up the peninsula. Having bottled the Polish units on the Peninsula, the Germans did not launch major land operations until the month’s last days.

On the night of 12/13 September, the remaining Polish light minelayers laid a minefield near Hel. On the following day, the Luftwaffe sank the Polish light minelayers Jaskółka and Czapla at the port of Jastarnia, while the remaining minelayers, Czajka, Rybitwa and Żuraw, were damaged. In view of German superiority in the Baltic Sea, the remaining Polish naval units docked at the port of Hel port and their crews joined the ground forces. The ships' guns were removed and adapted into additional land gun emplacements.

Heavier German naval units, namely the old pre-Dreadnought battleships Schleswig-Holstein and Schlesien, arrived and began to shell the Hel peninsula, but to little effect. Schleswig-Holstein began shelling Polish positions at Hel and Redłowo, on the other side of the Vistula Lagoon and site of the 'Battle of Gdynia', after the Polish garrison at Westerplatte surrendered on 7 September. These operations lasted until 13 September. Schlesien returned to bombarding the Polish positions at Jastarnia and Hel from 21 September. Between 25 and 27 September, Schleswig-Holstein joined her sistership at Hel once again. On 25 September Schleswig-Holstein was slightly damaged by Polish coastal batteries. Throughout that time, a number of air raids targeted the Hel Fortified Area. The Polish anti-aircraft batteries proved highly effective, shooting down between 46 and 53 German aircraft.

It is believed that the Germans, after initially being stalled by the Polish defences, brought up land artillery batteries and an armoured train battery to support their barrage. The German forces advanced slowly, still facing substantial resistance and counterattacks, and on 25 September, after the Germans had taken the village of Chałupy, Polish military engineers detonated torpedo warheads at the peninsula’s narrowest part, temporarily transforming the peninsula’s far end into an island.

A somewhat different account appears in some Polish writings, stating that no substantial land engagements took place until 28 September, when German units slowly advanced toward Chałupy. In this account, the major German push took place on 30 September 1939. The German units assigned to take Hel, the 374^th Infanterieregiment and the 207^th leichte Artillerieregiment, captured Chałupy on 30 September, and shortly afterward the Poles detonated the torpedo warheads, but the resulting damage was less than expected though it did wreck the peninsula’s railway line.

On 1 October, the Polish navy’s commander, Unrug came to the conclusion that the Polish outpost was running out of supplies and that no relief force would be coming, and in view of low troop morale (two attempted mutinies had been quelled on 29 and 30 September), ordered the Polish forces to surrender. Some Polish soldiers attempted to flee across the Baltic Sea to Sweden on the remaining light craft and civilian vessels, but most were unsuccessful. The Germans had occupied the whole of the Hel peninsula by 2 October.

Some accounts of the 'Battle of Hel' report the sinking on 1 October of the German minesweeper M-85 by a mine near the Hel peninsula, with the loss of 24 of her crew. The minefield had been laid by the Polish submarine Żbik as part of the 'Sack plan. Żbik and two other submarines, Sęp and Ryś, had been based at Hel and gone to sea on 1 September.

Polish battle casualties were light: some 50 men killed and 150 wounded. About 3,600 Polish soldiers and sailors were taken prisoner. The German losses were similar, estimated at a few dozen dead and wounded. Some remaining Polish light vessels, including light minelayers, gunboats and noncombatant units such as tugs that had not been in air raids, may have been scuttled before the capitulation. Either way, most were either captured by the Germans or raised from the shallow waters and pressed into German service in subsequent weeks.

After Hel’s surrender, the only organised military resistance in Poland was that of the Independent Operational Group 'Polesie', which capitulated after the 'Battle of Kock' on 5 October.