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Offensive and defensive use

While previous smaller guns could burn down structures with fire, larger cannons were so effective that engineers were forced to develop stronger castle walls to prevent their keeps from falling. Nonetheless, cannons were used other purposes than battering down walls as fortifications began using cannons as defensive instruments such as an example in India where the fort of Raicher had gun ports built into its walls to accommodate the use of defensive cannons. In The Art of War, Niccolò Machiavelli opined that field artillery forced an army to take up a defensive posture and this opposed a more ideal offensive stance. Machiavelli's concerns can be seen in the criticisms of Portuguese mortars being used in India during the sixteenth century as lack of mobility was one of the key problems with the design. In Russia the early cannons were again placed in forts as a defensive tool. Cannon were also difficult to move around in certain types of terrain with mountains providing a great obstacle for them, for these reasons offensives conducted with cannons would be difficult to pull off in places such as Iran.