People still send troops to the fortresses, you would be surprised.  You just have to find them ;)

Happy Hunting!  

Of course, smaller and new leagues trying to upgrade their forts are easy prey for the big leagues. But eventually, those smaller or new leagues learn that upgrading their forts is pointless and that sacrificing their units so the big leagues can score points is foolish.

Make sure that forts higher than level 20 are no longer protected, and that the big leagues, if they want to keep their forts at a higher level, have to reinforce them with their own units.

The big leagues would need many more units to defend their castle and all the beacons they're currently hoarding for themselves.

It does not matter the size of your league when you are upgrading your fortress.  It is a difficult task.  Bigger leagues, in order to reach level 30 need to hold 55 level 5 beacons.  Not many big leagues have the defense to securely hold that many beacons safely.

When we could only upgrade our fortresses to level 20, before this last upgrade, Level 20 was not safe.  Balur held more beacons on the map than leagues did because everyone put their defense into their fortress to protect the power the fortress gave to the league.  

The safe fortress levels are beneficial especially to small leagues as they can keep the power they get at the safe levels without losing it all.

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 These are the safe fortress levels.  Smaller leagues can build defense, upgrade to the next safe level.  They can keep or drop their beacons and get ready for the safe level if they want to. 

You can search online for a chart and find how many beacons you need for each level to upgrade your fortress.  There are a few of them out there.

As with everything in this game, it is a challenge and is not meant to be an easy task.  That is actually one of the things that I like most about this game.

Best of luck to you and your league in this task.