The document provides guidance on upgrading defenses as a Town Hall 9 player in Clash of Clans. It recommends the following order:
1. Mortar - does splash damage and looks impressive at higher levels, though it has a short range and low health.
2. Wizard Tower - shoots quickly and does splash damage, but has low health and short range.
3. Archer Tower - has high damage and very long range for both ground and air troops, but is expensive to upgrade and upgrade times are long.
4. Cannon - is cheap and quick to upgrade with a fair range, making it a good early investment.