I am in the middle of the last episode. The battalion has arrived in Baghdad and discovered that none of the military leaders have conceptualized the "big picture" of the US's goal.
Based on what I have read about the war (in particular Chandrasekaran's book Imperial Life in the Emerald City), this is an accurate depiction of one of the first of many US mistakes - a huge lack of big picture planning to guide our decisions in the initial weeks in the country.
There are a couple of especially compelling scenes where Nate Fick's platoon is sent out to neighborhoods that are just on the brink of descending into chaos; he has no orders/permission, though, to offer any humanitarian aid to the Iraqis (or really to do much of anything aside from make a sort of cameo show of force), and as a result the US troops generate confusion (and ill will) among the Iraqis more than anything else.
This episode includes the best line of the series and one that, I think, captures the riddle of the whole Iraqi invasion. The Rolling Stone reporter tells a soldier "I think I just saw an Iraqi, practically right next to me, get shot," to which the soldier responds "Too bad - he probably would have liked democracy."
