You're not telling the whole story, though. Ironically.
Lying in war is only permitted under duress, when your life is threatened for example. That's a point in favour of Islam. Lying to secure peace isn't exactly a good point of attack either. You're essentially arguing against a good thing. As for marriage, that's all you've got really. And it's more nuanced than simply 'lying is permitted in marriage'. It's something specific about slaves, but I can't be arsed to look it up.
Uh, not really, I practically translated the hadeeth word for word.
سمعت رسول الله صلى الله عليه وسلم يقول: ليس الكذاب الذي يصلح بين الناس فينمي خيرا أو يقول خيرا. وفي رواية: ولم أسمعه يرخص في شيء مما يقول الناس إلا في ثلاث: تعني الحرب، والإصلاح بين الناس، وحديث الرجل امرأته، وحديث المرأة زوجها.
(Sahih Bukhari and Muslim)
Anyway, I wasn't "attacking" Islam, just pointing this stuff out -- not making any judgments. There's another hadeeth that says, quite pithily, "War is deceit". And there's a third hadeeth that's used to justify lying in that situation that talks about how when Muhammad was travelling, and some dude from some opposing tribe saw him and asked him where he was from, he answered with a double-entendre that made the dude think he was from Iraq, when Muhammad "meant" that he was created "from water".