In July 1940, Great Britain and Germany came face to face. The armistice signed by the French government does not only deprive England of an ally which had undertaken, 3 months before, not to conclude any separate agreement with the Reich, it gives to the Kriegsmarine, at the time when it begins to develop its tactic of strangling trade, a seafront extending from the North Cape to the Spanish border, threatening the United Kingdom from the north, east and south; it also allows the Luftwaffe, which now has Dutch, Belgian and French airfields, to reach the heart of the British Isles. Having no army to oppose the Wehrmacht, Great Britain can only count for its survival on the still unbroken power of the Royal Air Force, and above all on the mastery of the seas which it confers - but for how many time ? - the overwhelming superiority of the Royal Navy.
It is in this tragic context that the problem of the French navy arises. Under the terms of the armistice of June 22, France can keep its warships under the control of Germany or Italy, the agreement stipulating only that they no longer take part in the fighting, nor alongside of England or against it. It is probable that Hitler and Mussolini, who counted on the power of the Italian navy, intended to respect this agreement. But Great Britain, which the defection of the French navy already places in a difficult position, cannot stake its existence on a presumption of this order. On July 3, the Admiralty launched Operation Catapult. French ships that have found refuge in British ports are seized by surprise by English sailors. Those who reached Alexandria were ordered to surrender and allowed themselves to be disarmed without resistance. But in Mers el-Kébir, all the negotiations fail. The Royal Navy opens fire on the French fleet, sinking 3 ships, killing or - wounding 1,650 sailors. This absurd drama, skilfully exploited by German and Vichy propaganda, turned almost all French sailors away from the resistance, almost all of whom asked to be repatriated, and turned French public opinion against Great Britain - at a time when de Gaulle, in repeated calls almost every day since June 18, asks all French people wishing to continue the fight to join him in London. Created on July 1, the Free French Forces (FFL), the Free French Naval Forces (FNFL) and the Free French Air Forces (FAFL) numbered only 7,000 men at the beginning of August, when the British government, having broken all relations with Vichy, recognizes Free France. At the same time, nearly 25,000 Poles, a Dutch brigade, 100 Norwegians, 800 Danes, 200 to 300 Belgians, a few hundred Czechoslovaks and several thousand Americans joined the British armed forces. But if the French of the metropolis were reluctant to engage alongside England, the territories of the Empire provided Free France with resources, bases, the beginnings of legitimacy and an embryonic army:between July and November 1940, the New Hebrides, the Ivory Coast, Chad, Cameroon, Tahiti, French New Caledonia and Gabon rallied to de Gaulle, who created the Empire Defense Council in October.
Despite the rallying of the French colonies and the participation in the war of the Commonwealth countries (with the exception of Ireland), the outcome of the conflict, once France is defeated, depends solely on Great Britain and its ability to resist German pressure. This can be exercised in several ways. A maritime blockade - assuming the Royal Navy could be defeated - would require a war of attrition lasting months or even years. For the problem to be solved more quickly, it is necessary that a German invasion force crosses the English Channel and lands in the south of England. On June 2, in the middle of the French campaign, Hitler asked the O.K.W. to examine under what conditions an operation against Great Britain would be possible. The O.K.W. proposed a 3-part plan, dubbed Operation Seelôwe (Sea Lion):neutralization of the R.A.F. by the Luftwaffe, control of the Channel by the Kriegsmarine (locking of the western Channel by minefields, creation of demined channels, fixing of the Royal Navy in the North Sea and the Mediterranean), then landing of a expeditionary coFps west of the Isle of Wight. But Hitler, who dreams of a world dominated by an Anglo-German coalition, is still reluctant to take the plunge. It was not until July 16, after Churchill had categorically - and it seems definitely - rebuffed his offers of peace that he asked the Wehrmacht General Staff to prepare Operation Sea Lion for mid -august. The deadline is too short. Raeder, aware of the weaknesses of the German navy, obtains that the operation be delayed for a month. Hitler and the O.K.W. bowed but set a deadline - September 17 - beyond which, due to bad weather, nothing could be done. On August 2, in his Directive No. 17, Hitler ordered the launching of naval and air operations against Great Britain and the constitution of an invasion fleet in the ports of the Channel and the North Sea.
In fact, the first air war in history - the Battle of Britain - began on July 10, when the Luftwaffe first launched large formations of fighters and bombers over Britain. The General Staff of the Luftwaffe has set itself a triple objective:to acquire mastery of the skies in the south-east of England (fighters), to destroy the economic infrastructure of the country (bombers), to prohibit the English Channel from merchant ships British (Ju-88 Stukas fighter-bombers). When Hitler asked Goering to move on to the second phase of the offensive, none of these objectives had been achieved. British fighters were not eliminated, far from it, and each English fighter shot down cost the Luftwaffe 2 aircraft. The bombardments of ports, fuel depots, communications centers were relatively ineffective. The Channel blockade has been in effect since July 25, but while UK merchant ships now have to bypass Scotland to reach the east coast, the Royal Navy still has a large fleet of torpedo boats, and this result has obtained at the cost of very heavy losses in fighter-bombers. A certain balance of power seems to have been established, but it is not possible to draw a precise conclusion, neither side having yet used all of its resources.