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Jan 1940 - Coastal Command aircraft are fitted for the first time with Air to Surface Vessel (ASV) radar detection sets and these were used primarily in the detection of German submarines.

1 Jan 1940 - The RAF introduces Identification Friend or Foe (IFF) signals to help identify Bomber, Coastal and Fighter Command aircraft on radar screens.

19/20 Mar 1940 - Bomber Command aircraft carry out their first attack on an enemy land target when 41 Whitleys and Wellingtons attack the German seaplane base on the island of Sylt. Post-attack reconnaissance of the night-time raid reveals no damage was done to the target, leading to a serious reappraisal of the Command's night navigation and bombing techniques.

April 1940 - Several large concentrations of enemy warships are reported in naval bases in the north during the first week of the month. Bad weather hampers RAF missions against them, and after a Sunderland flying boat reports German warships entering Trondheim fjord in Norway, it confirms allied fears of a German invasion of Norway which began on 9 April 1940. German forces also occupy Denmark whose forces did not resist the enemy invasion.

Apr-Jun 1940 - In the weeks following the German invasion of Norway, RAF bombers carry out bombing missions against enemy shipping and minelaying operations; on 7 May a Beaufort of Coastal Command drops the first 2,000lb (905kg) bomb during an attack on a German cruiser anchored off Norderney. Hurricanes of No. 46 Sqn based at Bardufoss and Gladiators No. 263 Sqn operating from HMS Glorious and the frozen lake at Lesjaskog provide support to the BEF in Norway. However, the BEF is evacuated in early June - the surviving Hurricanes and Gladiators being ordered to embark on HMS Glorious. Despite having no training in deck landing, all the Hurricane pilots land safely, but the carrier is intercepted and sunk by the German battleships Scharnhorst and Gneisenau during its return home. Only two RAF officers survive the sinking, one being the Officer Commanding No. 46 Sqn, Sqn Ldr K B B (later Air Chief Marshal Sir Kenneth) Cross.

10 May 1940 - Germany invades Holland, Belgium and Luxembourg as well as attacking French positions in Western France. The Luftwaffe flies more than 1,000 bombing sorties in support of the offensives. French and British fighters claim a total of 85 victories, but French indecision means that bombers of the Armee de l'Air (French Air Force) are not committed to action. Thirty-three RAF Blenheims attack German forces in Holland, losing 3 aircraft in the process. Later that day, 32 Battles attempt to attack enemy columns advancing through Luxembourg; 13 are lost to anti-aircraft fire and a further 10 shot down by fighters. During the night, Whitleys attack enemy communications in the RAF's first attack on mainland Germany. At home, Chamberlain resigns as Prime Minister. Mr Winston Churchill replaces him as head of a coalition government.

11 May 1940 - Seven out of eight Battles fail to return from an attack on enemy forces in Luxembourg. No. 114 Sqn's Blenheims are annihilated on the ground in a low-level German raid.

12 May 1940 - In an attack on the Maas bridges, four out of five Battles are shot down. Fg Off Garland and Sgt Gray are later posthumously awarded the first air VCs of the War.

13 May 1940 - In a speech to the House of Commons, Winston Churchill says, "I have nothing to offer..."

14 May 1940 - German forces break through the French front at Sedan. All remaining RAF Battles and Blenheims are ordered to attack pontoon bridges and troops in the area. Out of 71 aircraft, 39 are shot down - the highest loss in an operation of this size ever sustained by the RAF. A Luftwaffe raid on Rotterdam city centre by 57 He111s results in 814 civilian casualties and causes a massive outcry from neutral countries. Whilst the bombers were en route a delegation from the Dutch government was preparing to discuss surrender terms, but the attempt to call off the bombing by German commanders was only partially successful.

15 May 1940 - After a week of heavy fighting, the Dutch Army finally capitulates at 11 am. By nightfall, the RAF in France had lost 205 aircraft, including 86 two-seat Fairey Battles. During the night, RAF Bomber Command's air offensive against Germany begins - 99 aircraft attack industrial targets in the Ruhr. No aircraft are lost through enemy action.

17 May 1940 - Twelve Blenheims attack enemy tanks and troops near Gembloux. Ten are shot down by fighters and one by ground fire.

19 May 1940 - The rapid German advance now poses a threat to the remaining RAF aircraft in Belgium. Evacuation of the remaining squadrons is carried out over the next two days, and fighter operations over the battlefield are carried out by Hurricanes and Spitfires based in southern England.

26 May 1940 - Following the fall of Calais and Boulogne, Dunkirk remains the only port available for the evacuation of Allied troops from the Continent. No. 11 Group, under the command of Vice-Marshal Keith Park, assigns 16 squadrons to the protection of the port. During the evacuation (codenamed Operation Dynamo), a total of 32 participate, although they are rotated to provide rest periods and preserve aircraft for the inevitable defence of Britain.

27 May 1940 - The Belgian Army, hopelessly outclassed by the Germans, finally capitulates at midnight.

3 Jun 1940 - The last day of Operation Dynamo sees the RAF carry out 171 reconnaissance, 651 bombing and 2,739 fighter sorties. During the previous nine days, the RAF has lost 177 aircraft, including 106 fighters and the attrition is such that the first-line strength of Fighter Command stands at 331 Hurricanes and Spitfires with only 36 fighters in reserve. German aircraft also carry out the first attacks against Paris.

5 Jun 1940 - Small numbers of German bombers attack low-key targets in the east and south-east of Britain. These attacks are primarily to give crews navigational experience before the main assault on Britain.

10 Jun 1940 - Italy declares war on Britain and France.

11 Jun 1940 - The Fiat works in Turin are attacked by 36 Whitleys of No. 4 Group. The Italians make the first of seven attacks against Malta. The entire Maltese fighter defence of 4 Sea Gladiators only manages to damage one enemy aircraft. In North Africa, the RAF launches two raids against the Italian airfield at El Adem, Libya, destroying all 18 enemy aircraft on the ground.

18 Jun 1940 - The remnants of the RAF Hurricane squadrons in France evacuate their bases, having provided cover for the final Allied retreat from France; the last to leave are Nos. 1 and 73 Sqns, which had been the first to arrive in 1939. The fighting in France cost the RAF a total of 1,029 aircraft and over 1,500 personnel.

10 Jul 1940 - First phase of the Battle of Britain begins.

Click here to visit the Battle of Britain history site.

24/25 Aug 1940 - German bombs fall on central London for the first time. The following night, 43 aircraft from Bomber Command retaliate by bombing Berlin.

September 1940 - Air reconnaissance show a build-up of Italian forces in Libya preparing to attack Egypt. Blenheims of No. 202 Group attack enemy airfields and enemy shipping in Tobruk harbour. The Italian advance is halted several miles short of Sidi Barrani, just before the British defences at Mersa Matruh.

7 Oct 1940 - No. 80 (Signals) Wing is formed - the RAF's first electronic warfare unit.

9 Oct 1940 - The Western Desert Air Force is formed under the command of Air Vice-Marshal Arthur Coningham to conduct air operations in North Africa. Strength of the force amounts to three squadrons of Wellington bombers, five squadrons of Blenheims, three of Hurricanes and one Gladiator squadron. In addition, three squadrons of Lysanders are assigned to Army co-operation duties.

25 Oct 1940 - Air Chief Marshal Sir Charles Portal succeeds Air Chief Marshal Sir Cyril Newall as Chief of the Air Staff.

28 Oct 1940 - A new front is opened in the Mediterranean, when Italy invades Greece via Albania.

1 Nov 1940 - RAF and Fleet Air Arm aircraft attack targets in Naples and Brindisi on the Italian mainland and Albanian ports.

11 Nov 1940 - The RAF's first offensive air operations in Greece are carried out by Blenheims in a low-level attack on Valaca airfield.

13/14 Nov 1940 - Two aircraft of the Wireless Intelligence and Development Unit make the first direct attack on enemy Ruffian navigational radar installations on the Cherbourg Peninsula by homing in on their transmission.

14/15 Nov 1940 - 450 German bombers bomb Coventry with devastating effect.

14-23 Nov 1940 - RAF squadrons deploy from their bases in the Middle East to Greece under the command of Air Vice-Marshal J D'Albiac.

15-30 Nov 1940 - Blenheims and Wellingtons of the Western Desert Air Force attack targets deep inside enemy territory, and Lysanders and Blenheims provide complete reconnaissance of Italian defences at Sidi Barrani.

15 Nov 1940 - The prototype de Havilland Mosquito takes off for the first time; designed as a bomber fast enough to dispense with defensive armament, it has a top speed of 400 mph (644 km/h).

23 Nov 1940 - Seven Italian Caproni BR20m bombers, flying from bases in Belgium, are shot down by Fighter Command during an air attack on the UK.

24 Nov 1940 - The first trainees from the Empire Air Training Scheme arrive in the UK.

1 Dec 1940 - Army Co-operation Command is formed under the command of Air Marshal Sir Arthur Barrett.

9-15 Dec 1940 - The British counter-offensive in the Western Desert begins. Combined attacks by air, land and sea against troops and supply columns forces the Italians to retreat over the Egyptian border. During the offensive, British forces capture 30,000 Italian troops.

20 Dec 1940 - Two Spitfires of No. 66 Sqn carry out the first Rhubarb low-level fighter operations during an attack on Le Touquet, France.

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