It boils down to the way castles work now with everything being more alive and reactive than before. The environments really change things up since you can actually break through gates and walls to make your own paths, but the defenders aren't just gonna sit there they'll actively try to stop you by blocking chokepoints and setting up new defenses. Something interesting about infiltrating these places is how the weather plays into everything - rain helps mask your footsteps for sneaking around, and winter can be pretty brutal since it strips away vegetation you'd normally hide in plus those icicles can actually help create distractions when they fall.

The guards are definitely smarter this time around especially the samurai who'll actually dodge your smoke bombs and cut through bushes to find you, so you'll need to really think about upgrading those stealth skills. What's cool is how the patrols change their routines based on the weather, like taking shelter during storms which opens up new opportunities. You've got some nice options with the grappling hook for vertical infiltration, and you can get creative with stuff like throwing shuriken at lanterns to create darkness or using destructible objects for distractions.

Every assault ends up feeling different because of how all these systems work together, so you really need to stay on your toes and adapt your strategy as things change. Tip: pay attention to the weather forecast before starting a siege since it can make things either way easier or much harder depending on your playstyle.