The Blockade Game
In the course of the two major conflicts still active in the world today - the Russia-Ukraine and US-Iran wars - we have heard a lot about sanctions and blockades. Russian oil tankers and 'shadow' carriers have been sanctioned (and sometimes stopped and boarded), gas pipelines have been ruptured or turned off, and Ukraine's Black Sea grain ports have been repeatedly targeted by Moscow's missiles. In the Middle East, a US fleet is blockading the straits of Hormuz to prevent Iran exporting the oil that is its chief source of revenue, while Teheran simultaneously maintains its own chokehold over the region to stop Gulf oil getting out to the West. In both wars, these tactics (so far) have proved less than successful. In part, this is because sanctions (which are really a peacetime weapon) are an imperfect tool in today's globalised economy, while blockades rarely work effectively unless they're watertight - a tall order in a world where geo-political alliances are fragile and where 'shadow economies' have proved their resilience.
The 'Continental Blockade'
Blockades are a very old weapon of war. Because of British naval supremacy for most of the 19th and early 20th centuries, they were a favoured tactic in Britain's major wars during this period. In the Napoleonic Wars, France imposed its so-called 'Continental blockade' against Britain, in an attempt to stop British goods being imported into European countries occupied by or allied with France. This French blockade was itself a response to a British naval blockade of the French coast. But the Napoleonic blockade was simply too ambitious to work, with allies of the French turning a blind eye to widespread smuggling, and exclusively land-based customs checks at European ports proving ineffectual. As the Americans have found in the Gulf, the consequences of a blockade can be counter-productive and come back to bite you, especially if you don't have all the cards militarily (which the Americans don't right now). In the Napoleonic case, though British exports to the continent fell significantly, French ports suffered too and food prices rose across Napoleonic Europe. Moreover, British merchants made up for their losses by sharply increasing trade with the rest of the world - courtesy, once again, of their dominant sea power, a vital element in getting any blockade right. Ultimately, when Portugal refused to join the French blockade, then his ally Russia chose to reopen trade with Britain, Napoleon over-reached himself by invading both countries - with disastrous results: Wellington's successful Peninsula campaign followed and, in 1812, came the ignominious winter retreat of the Grande Armee from Moscow.
Britain's Blockade of Germany in WW1
In the First World War, Britain blockaded Germany with the warships of its Grand Fleet. For a time, the Admiralty contemplated a close blockade that would have sent its ships to patrol the German coast, even to go down the country's rivers. This was quickly seen to be too risky - the German High Seas Fleet was also formidable and German shore batteries could do considerable damage at close quarters. So the decision was taken to maintain a 'distance' blockade whereby the British Navy stopped German vessels trying to exit the Baltic into the North Sea and the Channel, and also patrolled a chosen line across the top of the North Sea (just below Scapa Flow) to prevent any German traders passing into the Atlantic. In the Gulf at the present time, the Americans have now also shifted from a close to a distance blockade, having moved their carriers well away from the Iranian coast, out of range of dangerous close-quarter counter-attacks. Given that oil tankers are slow and cumbersome, they cannot 'run' the US blockade, so the American adjustment is probably sensible. The trouble is that Trump claims this as a victory of sorts, when in fact it has not brought down soaring world energy prices (highly unpopular in the US) nor forced the Iranians to back down. So the stalemate continues and the war goes on.
Did the Allied WW1 Blockade Work?
The truth is, such blockades take a long time to work economically, if they ever work at all. In the First World War, after the (indecisive) 1916 battle of Jutland, Britain's blockade did at least stop the German fleet from venturing out of port again, but it took years to have the desired economic impact. Most historians today would probably agree that the blockade did contribute something to the Allied victory in WW1, not least by restricting the import into Germany of essential war materials such as oil and metal ores. The blockade did also prevent foodstuffs getting into Germany and here the issue becomes more contentious. The traditional view has been that by 1917, even by 1916 (when Germans endured the so-called 'Turnip Winter'), the German population at home was malnourished if not starving. This was blamed on the Allied blockade. By December 1918, according to the then German Board of Public Health, 763,000 civilians had died from starvation and related diseases. A further 100,000 were reckoned to have died between the armistice of November that year and Germany's signing of the Versailles peace treaty in June 1919, a period when the Allies maintained the blockade in order to make sure the Germans accepted the peace terms they were offered. There's a lot to unpack here and, on closer scrutiny, the reality looks rather more nuanced. In the first place, it's hard not to be sceptical about the German stats since, at the time, it was clearly in Germany's interest to promote high mortality figures in order to persuade the Allies to halt the blockade. We don't know how the German Public Health board arrived at its figures, but a Spanish flu pandemic, as well as bronchitis and tuberculosis outbreaks, were also killing tens of thousands of people in the same period. A 1928 academic study reduced the board's starvation figure to 424,000, with more recent scholars settling for a similar number or less.
German Food Production Declines
The other problem with attributing starvation to the Allied blockade is that it makes no allowance for other factors that were peculiar to Germany. Before 1914, the Germans produced 80% of their own domestic food needs (in contrast, the figure was a mere 35% for Britain, which was highly dependent on imports of food by sea). However, in the course of the war, Germany suffered a substantial deterioration in the calorific value of its food, mainly because German mobilisation for the war had a disastrous impact on agriculture. Robbed of the labour they needed, their horses commandeered, and lacking vital fertilisers (which were diverted to make explosives in munitions), German farmers significantly reduced their output (by 40%), leading to a substantial decline in food consumption. So it's been roughly calculated that only some 17.5% to 27.6% of this decline can be put down to the blockade - rather unhelpful figures if we want to be accurate but certainly not giving much due to the blockade. And that 'Turnip Winter'? Well, poor weather in Germany in the autumn of 1916 was catastrophic for the potato crop, as well as cereals, creating a scarcity of staple foods. So people resorted to turnips instead.
The Blockade of Japan in WW2
For a really successful blockade, the US submarine blockade of the Japanese home islands in the Pacific War makes for a telling (if less well-known) case study. Japan was densely populated (over 70m people in the 1930s) and particularly vulnerable to a sea blockade, for at the start of the war it was importing most of its raw materials, including all its oil, and a significant proportion of its foodstuffs, notably one third of its rice, which was imported from Japanese-occupied Korea and Formosa (today's Taiwan). This state of affairs reflected the shortcomings of Japanese agriculture, which was backward and inefficient, and as the war went on declined into subsistence cultivation. Even before Pearl Harbour, to stop Tokyo's expansionist ambitions southwards into Indo-China, the US had embargoed all oil going to Japan as well as other vital raw materials. In the early phase of the Pacific War, this US blockade was far from water-tight. This was partly because American subs were initially over-cautious and equipped with poorly designed torpedoes, many of which failed to detonate properly. However, by 1943 these and other technical issues had been rectified and the American submarine blockade became so effective that in November alone that year over 300,000 tons of Japanese merchant shipping was sunk; by early 1944, the figure was consistently 200,000 tons a month. In part, this was down to an extraordinary lack of interest from the Imperial Japanese Navy, which gave no priority to protective convoys or anti-submarine tactics (in stark contrast to the hard-fought battle of the Atlantic). The outcome was disastrous for Japan. In 1942, 40% of East Indies crude oil was getting through to the home islands; in 1943, that figure dropped to 15%, then 5% in 1944; in 1945, not a single drop of oil landed on Japanese shores. Effectively, this meant there was no fuel for Tokyo's planes, warships or factories. Also that food imports weren't getting through either. It didn't help that the fish catch (the major source of Japanese animal protein) fell by 50%. As a result, price inflation soared and widespread malnutrition took hold, not just among Japan's home population but affecting hundreds of thousands of its troops left stranded without supplies in mainland Indo-China or on far-flung Pacific islands. It's now estimated that 60% of Japan's 1.74m military deaths between 1941 and '45 were caused by starvation and related diseases - proportionately, a worse figure than in any other wartime country. By the time Tokyo finally surrendered, in August 1945, Japanese cities were facing famine.
If You Think You know About the Two World Wars, Think Again.
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