@Kubamorlo, Moros, Boomer:
There are lots of new card ideas (many of which have been proposed before / are already on UV). Of course you have every right to propose your ideas, but maybe it would be better to do so in separate threads? Otherwise this one could get quite messy.
(Also Boomer, that's a pretty misleading name; the entire idea of blitzkrieg is attacking the enemy when he's off-guard and/or deep into/behind enemy lines (impossible with standard WL rules / already accomplished by turning multi-attack on). Increasing kill rate has little to do with it; if I saw a blitzkrieg card I'd expect it to let (some subset of) my armies multi-attack in a game where that is otherwise not allowed. Especially when combined with dropping all your reinforcements into a single territory that turn, *that* would be worthy of the name "blitzkrieg".)
To increase your chances of people not "hijacking" your thread, it can help to put a very succinct description of your card in the thread title.
Ok, back on-topic. There are a few issues which need working out:
- If you lose a territory, then recapture it before the card expires, is it still valid? Technically you answered this with "would be null once someone else captured it". Then again, I am sure that means "the new owner does not take advantage of the card (and, is not limited by the no-attack clause)", but unsure whether it was *intended* to cover the recapture scenario.
- What happens when you play two of these on the same territory, do the effects stack (like multiple sanction cards)? Or is it simply not allowed, or...?
- To make things really interesting, have you considered allowing the kill rate to be increased above 100%?
- Do you just want to increase the defensive kill rate, or also lower the offensive kill rate? (Again, technically you've answered this, but I cannot know whether you thought about it and decided against it, or never even considered it.) Just going by the name of the card, lowering offensive kill rate makes even more sense than increasing defensive kill rate...
- Is this played at the start or end of a turn? Playing it at the start of a turn is much more powerful (you *know* it will be played when you still control that territory and it will be a nasty surprise for your opponents, who only see the Fortification when the turn plays out and they can't cancel their (potentially suicide) orders any more. Basically, I'm talking about the difference between [Abandon and Blockade cards](http://wiki.warlight.net/index.php/Abandon_Card_and_Blockade_Card
- While not extremely critical, if you can propose a way to mark fortified territories that would of course make your proposal sound that much better. :)