Siege ("a sitting down before") is the name given to a particular mode of attacking a fortified town which cannot be taken by surprise or by direct assault. The siege differs from a blockade in that the latter consists in simply preventing ingress to or egress from the city; though sometimes the two are combined, as in the case of the siege of Antwerp in the 16th century. The first thing necessary in establishing a siege is to overpower any out1ying forts that might harass the attacking party. Batteries are then established within easy cannon-range, and the attack is opened. Meantime a gradual advance is made upon the stronghold by means of trenches, which are protected at intervals by parallels, and which are carried on by zig-zags, so as to avoid being swept by the enemy's fire. In the case of a moat, mining is employed if possible. Provision is made in the trenches and paral1els for accommodating a sufficient number of troops to repel any sortie attempted by the besieged garrison. When a breach is made in the walls by mining or direct battery, the assanlt is delivered. There were memorable sieges in the Peninsular War; and in later times those of Sebastopol, in the Crimean War, and of Paris, in the Franco-German War, were of much importance.