Cannons
Cannons are ideal for the defense position, so you should improve your cannons to increase their firepower, but remember that they cannot be fired during the process of improvement. The barrel is the first defensive structure that a player will receive at the beginning of Clash of Clans. It is cheap and its improvement is quick to level 11.
Cannons have a power of rapid fire and a good range being good defense against fire.
Cannons are also useful to keep the Giants away from other defenses. Defend your mortars and your Wizards Tower by placing them in the action area of your cannons and ensure to place your cannons in range of your air defenses because cannons cannot attack flying troops, so you have to improve your as mortars as your main defensive structure.
They aren’t able to target flying troops which leaves them defenseless against gargoyles, balloons or dragons if they are not in range of your air defenses. The cannons can attack a unit at a time. This easily makes them vulnerable against a group of archers or barbarians. Even with these flaws, remember that the cannons have a good firing frequency.
There is a significant visual change in the improvement of the cannon to level 7and they undergo remarkable visual changes for level 7 to 12.
Mortar
The mortar can wipe out the hordes of enemies with powerful explosion and don’t let the enemy get close.
The mortars are deployed among the defense and when an enemy enters their firing range, they project into the air a ball that explodes on contact with the ground.
Mortars cause powerful AoE damage, but take every 5 seconds. Their AoE damage combined with their long reach make mortals against the troops of Tier1 like barbarians, Archers and Goblins. A major constraint of Mortar is the inability to attack a nearby enemy within 4 blocks.
Mortars do not attack flying targets.
Mortars should be logically the center of your town behind Walls. Their long reach allows them to attack behind the structures. Since they cause area damage, they can quickly decimate the enemy troops.
Several mortars enable a greater fire power.
Be careful when you improve as some players take this opportunity to attack you.
Mortars with their low rate of fire and ineffective against the flying Troops make them vulnerable defenses against certain types of attack.
Rapid troops as barbarians or Goblins, once all resources Buildings are destroyed, can rush to the area where the mortar cannot attack.
The Archers are also effective against Mortars if they are positioned in a circle around it.
Mortars have relatively few points and, therefore, are vulnerable against the Giants.
You can also send small groups of barbarians to distract mortars while Goblins or Archers destroy the buildings.
