your Town Hall offensively is of utmost importance for war
matchmaking. This means that you must max out your war troops
before going to the next level Town Hall. Upgrade your walls to
the best of your ability.
must have a level 5 Barbarian King before upgrading to TH8.
must have a level 10 Barbarian King before upgrading to TH9.
must have a level 20 Barbarian King and a level 20 Archer Queen
before upgrading to TH10.
you have recently upgraded your Town Hall you must prioritize
upgrading your spell factories, clan castle, army camps,
barracks, and heroes before upgrading defenses.
reason why offense must take priority for recently upgraded Town
Halls is because the transition from the previous Town Hall
to the next Town Hall is very stressful for wars. You will need
to attack higher level bases that you wouldn't have had to
attack in the previous Town Hall.