The First World War opened without immediate effects on agriculture, except tha t the needs of the army soon began to weaken the industry’s resources. Skilled farmworkers, together with estate workers and village blacksmiths, wheelwrights and carpenters, were allowed, indeed encour aged, to join up, and horses were taken from the stables of manor houses and farms to satisfy the demand for remounts and haulage animals. I t was not until almost the end of 1916 that indiscriminate recruiting was seen to be a mistake, and the urgency of expanding home production of food was appreciated. The harvest in North America proved to be a poor one that year, but a more immediate problem was the effect of the shipping losses tha t threatened to starve the country of food and essential war supplies. At the outbreak of the war Britain had imported four-fifths of its cereals, two-fifths of its meat and threequarters of its fruit, to say nothing of all its sugar and colonial produce and large proportions of other foodstuffs. The German U-boats found the slow, unarmed merchant vessels easy targets, and although the belated introduction of convoys guarded by warships — a system used to counter the depredations of French privateers in the Napoleonic Wars - reduced the losses, shortages of food, fuel and other vital imports became critical to the fighting of the war.