The battle began with German air attacks, continued with the landings on 12 November, and ended with the capitulation of the Allied forces four days later.

During Italian rule, Leros, with its excellent deep-water port of Lakki (Portolago), was transformed into a heavily fortified aeronautical and naval base, "the Corregidor of the Mediterranean", as Mussolini boasted.

In addition to that, air cover was minimal, with the U.S. and British aircraft based in Cyprus and the Middle East, a situation which was to be exacerbated by the withdrawal of the American units in late October in order to support operations in Italy.

As the Italian surrender became apparent, German forces, based largely in mainland Greece, were rushed to many of the major islands to gain control.

The most important such force, the Sturm-Division Rhodos [de] swiftly neutralised the garrison of Rhodes, denying the island's three airfields to the Allies.

On 3 October, the Germans effected amphibious and airborne landings (Unternehmen Eisbär, 'Operation Polar Bear'), reaching the outskirts of the island's capital later that day.

[1] The vast majority of these men – 6,065, plus an additional 697 militarized personnel – belonged to the Royal Italian Navy, as Leros was mainly a naval base.

After the fall of Rhodes, some men from its garrison reached Leros, and Mascherpa assumed command of all Italian naval forces in the Aegean Sea.

On the following day, more British officers arrived, including Major George Jellicoe and Colonel Turbull, who was disappointed by the state of the defences, particularly the anti-aircraft preparations.

Initially, the British had planned to secure the high ground of the island's interior, but Brig Tilney insisted on a forward defence on the coastline, which had the effect of spreading his forces too thinly.

On the night between 6 and 7 October, in the Astypalaia channel, the Royal Navy cruisers Sirius and Penelope and the destroyers Faulknor and Fury attacked a German troop convoy consisting of the auxiliary submarine chaser Uj 2111 (former Italian gunboat Tramaglio), the cargo ship Olympus and seven Marinefährprahme (MFPs), sinking all but one MFP.

[1] Starting on 26 September, after days of dropping threatening leaflets, the Luftwaffe unleashed continuous attacks on Leros, enjoying complete air superiority.

[1] Mascherpa was not forewarned of the substitution; he was asked to go to Cairo to discuss the situation on the island, but he refused, fearing that he would not be allowed to go back to Leros to lead the defense.

[1] The British commando even asked for Mascherpa to be substituted, and Supermarina decided to replace him with Captain Dairetti, but this was never carried out due to subsequent events.

[1] On 7 November, the Luftwaffe bombings started again; over the next five days, a total of 187 German bombers carried out 40 raids over the islands, especially targeting the batteries located on the eastern part of the island (the area designated for the main landing) and those in the central and southern part (so that they would stop firing against Kalimnos), as well as the Anti-Aircraft and Coastal Defense Command (aiming to destroy coordination between the batteries) and the area of Lakki and Mt.

[1] On 12 November 1943 at 04.30, after almost fifty days of air strikes, an invasion fleet landed troops at Palma Bay and Pasta di Sopra on the north-east coast.

[1] In the central part of the island the Germans, despite counter-action, managed to create small bridgeheads and in the afternoon, after heavy fighting, they captured the Italian Ciano battery on Mount Clido.

[20][21] Heavy fighting developed around the Lago battery (commanded by Sub-Lt. Corrado Spagnolo, who was killed in action), defended by its gunners and by an Italian Navy platoon sent as a reinforcement in a hand-to-hand combat.

In the early afternoon Luftwaffe fighter-bombers machine-gunned and bombed the area between the Gurna and Alinda Bays, followed by Junkers Ju 52s which at 13:27 dropped some 600 parachutists from the Brandenburg Division over Mount Rachi.

Counterattacks by the King's Own and the Fusiliers failed during the 13th with heavy casualties, but the Buffs on the south side of the island managed to capture 130 prisoners and reclaim some control of their area.

[1] The Ciano battery, attacked by German forces supported by Luftwaffe planes, resisted until all the guns were put out of action; after capture, its officers were executed.

On the night of 14 November two more companies of the Royal West Kent Regiment and their commanding officer, Lt Col Ben Tarleton, from Samos landed at Portolago Bay.

British counterattacks on that day were sporadic and carried out by fragmented forces, thus resulting ineffective and weakening the central sector of the island; however, with the help of two Royal Navy destroyers, it was possible to recapture the Ciano battery, taking over 230 prisoners.

German forces attacked the castle; the commander of the local British platoon ordered it to be abandoned, but Italian Navy personnel instead kept defending it.

[1] During the night Lt. Col. John Richard Easonsmith, commander of the Long Range Desert Group, was killed in action while fighting inside the town of Leros.

Maraviglia was attacked by German forces but stiffly defended by its garrison, commanded by Captain Werther Cacciatori, who lost an arm.

[1] On the morning of 16 November it became apparent to the British commander, Brigadier Tilney, that his situation was untenable; at 17:30, when German forces had nearly reached his headquarters, he decided to surrender.

The Commander-in-Chief (C-in-C) of the British Ninth Army, General Sir Henry Maitland Wilson, reported to the Prime Minister: "Leros has fallen, after a very gallant struggle against overwhelming air attack.

Everything was done to evacuate the garrisons of the other Aegean islands and to rescue survivors from Leros, and eventually an officer and fifty-seven other ranks of the 1st Battalion, King's Own Royal Regiment (Lancaster) rejoined the details in Palestine.

Along with the occupation of the smaller islands of Patmos, Fournoi and Ikaria on 18 November, the Germans thus completed their conquest of the Dodecanese, which they were to continue to hold until the end of the war.