"While paintings, poems, films and histories memorialise the great naval battles – Salamis, Lepanto, Trafalgar, Midway – when one navy destroyed another, the main strategic purpose of navies is to control the seas, and the highways that criss-cross them, and prevent their enemies from doing so. Even today land communications are vulnerable to disruption, either man-made or natural; how much more so in the past before surfaced roads and railways? Ever since humans began to build floating craft, water has been the most reliable way of moving people and material. Navies exist to protect their nations, their coasts, people and shipping, and to project their power abroad. By landing troops on enemy coasts, acting as floating gun and aircraft platforms in more recent times to bring firepower to bear on land targets, or destroying enemy capacity to wage war, whether by sinking or seizing enemy and sometimes neutral shipping or blockading ports so that needed resources, including soldiers, cannot move in or out, a powerful navy can make it difficult, even impossible, for its enemy to wage war on land or at sea. ‘We destroy the national life afloat,’ said the leading British naval theorist Julian Corbett, who taught generations of officers before the First World War, ‘and therefore check the vitality of that life ashore, as far as one is dependent on the other.’"