Berlin, Germany September 17, 1940

In November 1939, some two months after Germany had invaded Poland, Grand Admiral Erich Raeder, head of the Kriegs­marine, in­structed a subordi­nate to draw up a paper on “the pos­si­bility of troop landings in Eng­land.” The study paper set out four pre­requi­sites. The next month the German Army, with input from the Kriegs­marine and the Luft­waffe, issued its own paper, also laying out four pre­req­uisites. The sub­stance of both papers presumed the success­ful elimi­na­tion of the Royal Air Force in English skies and the sealing off or the elimi­na­tion of the Royal Navy from English landing and approach areas before launching an invasion.

Following Germany’s swift occupation of the Netherlands, Belgium, Luxem­bourg, and France in May and June 1940, and Adolf Hitler’s growing impa­tience with British indif­fer­ence toward his recent peace over­tures, the German leader for­mally set in motion pre­para­tions for Opera­tion Sea Lion (Unter­nehmen See­loewe), the cross-Channel inva­sion of Eng­land from ports in the Low Countries. Sadly for Germany, the fail­ure of Hermann Goering’s Luft­waffe in August and Septem­ber 1940 to defeat the Royal Air Force (one of the four prereq­ui­sites) during the height of the Battle of Brit­ain, despite inflicting punishing losses on British air­craft and crews, con­vinced the Kriegs­marine’s high com­mand that the seaborne inva­sion of England was too risky. Not being certain of the approaching winter weather, Hitler wisely decided on this date, Septem­ber 17, 1940, to post­pone the invasion until a new date could be set.

The Luftwaffe still had orders to continue its attacks on Britain. Instead of air­fields and other mili­tary instal­la­tions, the Luft­waffe now tar­geted indus­trial cen­ters and, finally, on Septem­ber 7, 1940, the city of London itself. This phase of the air war over Britain was called the Blitz (Septem­ber 7, 1940, to May 10, 1941) and was Hitler’s way of pun­ishing the Brit­ish for refusing to sur­render. Assisting the Luft­waffe in pun­ishing Eng­lish cities was a small con­tin­gent of Ital­ian fighters and bombers, the Ital­ian Air Corps (Corpo Aereo Itali­ano, or CAI), which over a 100‑day period had little to show for its effort, earning the mocking nick­name “The Chianti Raiders” whenever RAF pilots acted to intercept the incoming aircraft of Hitler’s Axis ally.

The Battle of Britain (July–October 1940)—the air war that was Opera­tion Sea Lion’s pre­landing phase—was pretty much a draw. The Germans lost approx­i­mately 1,686 air­craft and 2,600 air­crew to the British 1,643 air­craft and roughly the same number of air­crew. That said, the Luft­waffe’s failed air cam­paign to sub­due the island took the wind out of Sea Lion’s sails. This was a god­send for Great Britain. After the evac­u­a­tion of the British Expe­d­ition­ary Force to England in late May and June 1940 from Dunkirk and other French ports the shell-shocked British Army was little more than a “card­board force” inca­pa­ble of reversing an amphib­ious and air­borne inva­sion much less dislodging a vet­eran and well-trained enemy once it was firmly estab­lished on English beach­heads. Hitler’s am­bit­ions for domi­nating Europe now turned toward the Soviet Union, which was 2 years into a 10‑year non­aggres­sion pact (Molotov-Ribben­trop Pact) with an incor­rigible aggres­sor and shame­less back­stabber. Opera­tion Barba­rossa, launched on June 22, 1941, proved a fatal mis­take. In less than four years the capi­tal of Hitler’s Thou­sand-Year Reich, menaced on every side by Soviet land forces and over­head by Anglo-American bombers, had shrunk to a few hun­dred square yards, becoming the Nazi leader’s tomb on April 30, 1945.

The Battle of Britain Halts Operation Sea Lion, the 1940 German Invasion of England

Barges being readied for Operation Sea Lion, Wilhelmshaven, August 1940German Pionierlandungsboot 39, Soviet Union, 1941

Left: Lacking purpose-built landing craft, the Kriegs­marine impro­vised with in­land freight barges in the lead-up to Opera­tion Sea Lion, as shown here at Wilhelms­haven, Germany, August 1940. Approxi­mately 2,400 barges were col­lected from all over Nazi-occupied Europe (half from the Nether­lands). Of these only about 800 were powered (some poorly); the rest had to be towed by tugs. Converting the assembled river barges into landing craft for troops, tanks, and vehicles was compli­cated. Some barges could accom­mo­date three or four tanks. After Sea Lion was can­celled, the Kriegs­marine used some of the moto­rized barges for landing on Soviet-held Baltic islands but most were returned to their former service.

Right: In the late 1930s the Kriegsmarine ordered the develop­ment of pur­pose-built landing craft, which were tested in the Baltic Sea begin­ning in March 1941. Not until Septem­ber 1941, a year after Sea Lion was can­celled, was the first in a series of landing craft, the Pionier­landungs­boot 39s shown here on the Russian Front, avail­able for service. Excepting the last in the series, the “Pilabos” were assembled from two mir­rored pieces, which could be trans­ported by rail to the coast or river entry. The Pionier­landungs­boot 39 was nearly 50 ft long and 15 ft wide and cap­able of carrying 20 tons. It was first used during Opera­tion Bar­ba­rossa, Hitler’s inva­sion of the Soviet Union. The largest and last in the series of landing craft, the three-piece Pionier­landungs­boot 43, was 116 ft long, 28 ft wide, capable of carrying 95 tons of cargo, and sported a light antiaircraft gun.

He 111s over Britain, 1940London docks and warehouses burning, September 7, 1940

Left: German twin-engine bombers (He 111s) over Britain. From the per­spec­tive of Germany, the fifteen weeks of aerial com­bat known as the Battle of Brit­ain (July–October 1940) was an attempt to whittle away at the Royal Air Force, there­by giving the Luft­waffe air supe­ri­ority during Opera­tion Sea Lion. Stymied by the RAF on the one side and by their own lack of com­bined opera­tional com­mand on the other, the Germans switched from bombing mili­tary com­plexes to bombing cen­ters of indus­try and popu­lation, inadver­tently per­mitting the RAF to regroup and replace its lost aircraft and installations.

Right: The first heavy bombing of London’s docks came on the night of Septem­ber 7, 1940 (“Black Satur­day”), which was the start date for the London Blitz. A third of Britain’s over­seas trade passed through the London docks, the beating heart of the island’s trade and imports. The aerial pounding by 967 German and Italian fighters and bombers, which dropped 600 tons of high explo­sives and 17,000 incen­di­aries, lasted eight hours. The huge pall of smoke bil­lowing from river­side ware­houses and docks could be seen for miles. Fires raged right up to Tower Bridge. When the “All Clear” sounded and survi­vors emerged from shelters into the dust- and smoke-filled streets, some 1,000 Lon­doners were dead, another 1,600 seriously wounded, and the rest of the capital’s inhabi­tants numb with shock. Like the Battle of Brit­ain, the Blitz never achieved its intended goals of either demor­al­izing Brit­ish poli­tical and mili­tary leaders into capit­u­la­tion or signi­fi­cantly damaging the coun­try’s eco­nomy to con­tinue the war. (Over its nine months, the Blitz killed more than 43,000 civil­ians.) By the time the last bombs had fallen on Lon­don on May 10, 1941, in a par­tic­u­larly murderous cli­max to the Blitz, the inva­sion threat had passed, and Hitler’s atten­tion was directed eastwards to the Soviet Union.

Great Blunders of World War II: Operation Sea Lion, The Mission That Never War