Churchill presents a strategic view in which defence begins not at a country’s own coastline but at the point from which an enemy can project military power. In a naval context, the enemy’s port is the base from which warships can be supplied, repaired and deployed. Watching, containing or threatening that base can therefore reduce the danger before hostile forces reach home waters.

The statement reflects the idea of forward defence: security may depend on acting at a distance rather than waiting for an attack to arrive. It also suggests an offensive element within defensive strategy, since protecting one’s own territory may involve placing pressure on an opponent’s military infrastructure. The principle does not mean that attacking enemy bases is always desirable or effective; its value depends on circumstances, capabilities and wider political aims. More broadly, the quote illustrates how strategists may define defence in terms of preventing threats from developing close to home.