besiegers. In response to the vulnerabilities of star forts, military engineers evolved a much simpler but more robust style of fortification. A polygonal fort is a fortification in the style that evolved around the middle of the 18th century, in response to the development of explosive shells. The complex and sophisticated designs of star forts that preceded them were highly effective against cannon assault, but proved much less effective against the more accurate fire of rifled guns and the destructive power of explosive shells. The polygonal style of fortification is also described as a "flankless fort". Many such forts were built in the United Kingdom and British Empire during the government of Lord Palmerston, and so they are also often referred to as Palmerston forts. Fort Tas-Silġ is an example of a British polygonal fort. Firearms The power of aristocracies vis à vis states diminished throughout Western Europe during this period. Aristocrats' 200- to 400-year-old ancestral castles no longer provided useful defences against artillery. The nobility's importance in warfare also eroded as medieval heavy cavalry lost its central role in battle. The heavy cavalry - made up of armoured knights - had begun to fade in importance in the Late Middle Ages. The English longbow and the Swiss pike had both proven their ability to devastate larger armed forces of mounted knights. However, the proper use of the longbow required the user to be extremely strong, making it impossible to amass very large forces of archers. The proper use of the pike required complex operations in formation and a great deal of fortitude and cohesion by the pikemen, again making amassing large forces difficult. Starting in the early 14th century, armourers added plate-armour pieces to the traditional protective linked mail armour of knights and men-at-arms to guard against the arrows of the longbow and crossbow. By 1415, some infantrymen began deploying the first "hand cannons", and the earliest small-bore arquebuses, with burning "match locks", appeared on the battlefield in the later 15th century. Decline of plate armour In virtually all major European battles during a period of 250 years (1400 to 1650), many soldiers wore extensive plate armour; this includes infantrymen (usually pikemen) and almost all mounted troops. Plate armour was expected to deflect edged weapons and to stop an arquebus or pistol ball fired from a distance, and it usually did. The use of plate armour as a remedy