How to keep the borders safe?

[Taqwus]

Remote summons (e.g. Army of the Dead, Call of the Wild, Angelic Host, Imprint Souls et al) can also help somewhat.
Don't forget the leader-killing spells, too; Earth Attack, Seeking Arrow, Mind Hunt and such. If the army has no leaders, it can't move.

[HJ]

Thanks for the tips. I guess I have to adjust my strategies to this porous nature of borders a bit. Whenever I can focus my forces on one side sufficiently, I have no problems, but when they employ the termite strategy, I lose ground and money and get pushed back. I guess I'm being to straightforward and expect them to do the same.
Cheers,