[9] The German army high command (Oberkommando des Heeres (OKH)) was preoccupied with the forthcoming Operation Barbarossa, the invasion of the Soviet Union and was largely opposed to an attack on Crete.

No Royal Air Force (RAF) units were based permanently on Crete until April 1941 but airfield construction took place, radar sites were built and stores delivered.

[17] A radar station was established on Ames Ridge, a hill south east of Heraklion airfield, but it was outside the defensive perimeter and its communications were unreliable.

[30][note 1] The German assault on Crete was code-named "Operation Mercury" (Unternehmen Merkur) and was controlled by the 12th Army commanded by Field Marshal Wilhelm List.

They totalled 22,000 men grouped under the 11th Air Corps (XI Fliegerkorps) which was commanded by Lieutenant-general Kurt Student who was in operational control of the attack.

[35] A few days before the attack, German intelligence summaries stated that the total Allied force on Crete consisted of 5,000 men and that the garrison of Heraklion was 400 strong.

The static lines, which automatically opened the parachutes as the men jumped from the aircraft, were easily fouled and so each man wore a coverall over all of their webbing and equipment.

[39] The danger of fouling the static lines also required that German paratroopers leapt headfirst from their aircraft and so they were trained to land on all fours – rather than the usually recommended feet together, knees-bent posture – which resulted in a high incidence of wrist injuries.

Given the importance of landing close to one of the weapons containers, doctrine required jumps to take place from no higher than 400 feet (120 m) and in winds no stronger than 14 miles per hour (23 km/h).

The regiment's 3rd Battalion (III/1) would land in the open areas south west of Heraklion, rapidly concentrate and take the town by a coup de main.

[47] After capturing the airfield and town Bräuer intended to move his regiment west towards the Germans landing 80 kilometres (50 mi) away at Rethymno, while deploying a scouting screen eastwards.

[50] They were blanketed with dust clouds blown up by the aircraft's engines, reducing safe taxiing speeds and making taking off and landing hazardous.

[35] Both the infantry and the anti-aircraft guns were under orders not to return fire, so the attackers were unable to identify their positions and there were few casualties among the well dug in and camouflaged Allies.

[35] Due to a failure of wireless communications, the 14th Brigade was unaware of the airborne assault in western Crete that morning and did not associate the unusually heavy air raid with the possibility of a parachute attack.

The German battalion commander, Major Karl-Lothar Schulz, attempted to regroup in the southern part of the town but was unable to recall all of those fighting in the narrow streets.

Determined, in the words of the historian Callum MacDonald, "to snatch victory from the jaws of defeat" he ordered that all resources be reallocated to capturing the airfield at Maleme, 100 miles (160 km) west of Heraklion.

[67] At nightfall on 20 May an Allied naval squadron known as Force C and consisting of two cruisers, HMAS Perth and HMS Naiad, and four destroyers, commanded by Rear Admiral Edward King, entered the Aegean via the Strait of Kasos to the east of Crete.

Aware of the convoy's progress due to Ultra signals intercepts the Allies sent a squadron through the Kythira Strait to the west of Crete.

The British squadron attacked the head of the by now scattered convoy, harried by the Italian torpedo boat Lupo, which was hit repeatedly and driven off.

Not finding any shipping the squadron searched to the west and intercepted the main escort of the 2nd Motor Sailing Flotilla, the Italian torpedo boat Sagittario, at 10:10 and approximately 25 miles (40 km) off Milos.

King's warships, despite their failure to destroy the German troop transports, had succeeded in forcing the Axis to abort the landing by their mere presence at sea.

He requested reinforcements from the II/2 Battalion, but this unit had heard that its missing components had been diverted to Maleme and, facing large bands of armed Cretan civilians, only sent one platoon.

After Heraklion was heavily bombed the III/1 Battalion attacked the shaken Greeks via the South and West Gates, broke into the town and relieved some of the paratroopers isolated the previous evening.

73 Squadron RAF were sent to Heraklion from Egypt, but several suffered landing damage and the facility lacked adequate fuel and ammunition for them and they were withdrawn the next day.

On the 24th four companies of paratroopers were dropped west of Heraklion to reinforce the Germans[81] and the town was heavily bombed in retaliation for its non-surrender on the 21st and again on the 23rd; according to MacDonald it was reduced to rubble.

[31] Middle East Command and the Allied HQ on Crete's plan was that when the Argylls arrived at Heraklion, one of 14th Brigade's existing battalions would move westwards to Rythymno.

Chappel, believing the German force to be stronger than it was, was content for the brigade to hold its positions, although several tanks and some artillery pieces were sent by sea to the more active fighting in the Maleme area.

[90] Shortly before noon on 28 May a further 2,000 paratroopers landed to the east of the brigade's position and late that afternoon the Allies were heavily bombed for two hours.

The naval evacuation force consisted of three cruisers – Orion, Ajax and Dido – and six destroyers – Hotspur, Jackal, Decoy, Hereward, Kimberley and Imperial – and was commanded by Rawlings.

[91] Before reaching Heraklion Ajax suffered a near miss from a bomb, which started a fire on the ship; Rawlings ordered her back to Alexandria.