Board Thread:Questions and Answers/@comment-71.165.41.11-20150709172111/@comment-26215551-20150709191302

Your swords are certainly high level enough - I believe the problem is your Wakis and Uchigatanas. Even at the same level as your Tachis and Oodachis, they will be weaker (deal less damage AND receive more enemy damage). Since it seems like you're losing troops, I would recommend either 1. equipping them with shieldmen (high HP + boosts defense), or 2. swapping them out for other Tachis and Oodachis. If you swap them out, you'll have to take the time to level up your new swords, but it'll be worth the investment in my opinion. (Your Wakis and Uchigatanas will be helpful on World 6, however!)