@Wolfshanze:
Ya, there is another game called āShogunā by Queen Games.
https://boardgamegeek.com/boardgame/20551/shogun
But itās totally different than the Milton Bradley āShogunā
https://www.amazon.com/Milton-Bradley-Shogun-Gamemaster-Series/dp/B001NHE7BW
Which was later renamed āSamurai Swordsā and released by Ikusa
https://www.boardgamegeek.com/boardgame/221/ikusa
And is now entirely out of print 
I had the original Shogun that mysteriously disappeared in my teens.
Several years ago I picked up Ikusa. Itās the same game, with āupgradedā art, but no little plastic swords (#sadface). I was sad to find itās now unavailable to purchase new.
@Private:
I would say that the key is to always use your daimyo armies to the full AND then make sure they are safe at the end of the turn.
Defending borders with non-daimyo garrisons and castles can be expensive and yet ineffective. A better defense is the threat of counterattack by your own daimyo. And a better use of castles can be to provide your daimyo army with a safe haven.
The loss of a daimyo army is a significant set-back. The biggest threat is a two or more daimyo attack on one, so always beware this from your opponents and try to create such a possibility for you.
Lastly, the fluid alliances of this game make the diplomatic aspect critical. If any player looks like winning, it makes sense for the others to gang up on him/her. So if you can surprise your opponents with the win, so much the better. For example by going first. Or by taking out an opponent.
Pretty much this. Iāve never found a strategy that I have stuck with but this advice is golden.