A typical
military confrontation in
medieval times was for one side to lay seige to their opponent's
castle. When properly defended, these high walled fortifications were virtually impenetrable to
infantry or
cavalry. The attacker then had the choice of simply surrounding the castle and blocking food deliveries and waiting for the defenders to surrender in the face of starvation, or more proactively to employ war machines specifically designed to destroy or circumvent castle defenses.
The most famous example would be the
catapult and its many versions, such as the
ballista and
trebuchet. These machines used mechanical energy to fling large projectiles to batter down stone walls. Also used were wooden towers on wheels, that allowed attackers to climb up and over castle walls, while protected from enemy arrow fire.
Other tactics included setting fire to castle walls in an effort to melt the cement that held together the individual stones so they could be readily knocked over. Another indirect means was the practice of sapping, whereby tunnels were dug under the walls to weaken the foundations and destroy them.