I forgot that one. The IG doctrines were great. When I first began building my Guard army it was with that codex. Chapter traits or doctrines were awesome because you could create a very specialized army to suit your playing style and needs. I built a very good Marine army using the traits. At the time I was also strapped for cash. And I managed to use the doctrines in such a way I was able to still build a potent army without spending a vast fortune on it. And when that codex was invalidated so too was that army. Pretty much had to break down most of the models and redo everything. And then spend more cash to get more stuff to make it strong. My Guard army luckily wasn't hurt by the invalidation of the doctrines codex.