I'm posting a link to 'Master At Arms' by Hokuto, with the author's permission. I stumbled across it quite serendipitously just a couple of hours ago, and for all that it's absolutely amazing, I was shocked to see no comments whatsoever, though it's been around on AO3 for a couple of months or more.

This is, I suppose, a rec, but I just want it to circulate more, and I imagine that while some of you may have come across it, many more haven't. It's the story of the Time War and the Master's place in it, a brilliant character study and a truly terrifying look at just what the Time War might mean, both to the Universe at large and the people fighting in it. It doesn't ignore the horrors, or pretty things up. 

Although it's gen, the mentions of the Doctor are written in such a way that it is, for me, very easy to read a relationship into it, whether that was the author's intention or not. Oh, and there's Susan! And SIDRATs!

I just discovered that the author is also on lj as brief_transit ! Anywho, here's the link at AO3: archiveofourown.org/works/85429

And here it is at the author's lj:  http://brief-transit.livejournal.com/72602.html

No rating given, but there's certainly violence and darkness and, you know, depictions of war, so I'd say around PG-13. Anyway, go! Read it!