I am no fan of Mike Brown; I'm not sure who has tried to mitigate or excuse his failure. However, I have said that Chertoff is more culpable and in many respects Brown gets a bad rap. (Ironically, I am not the only one who feels that way. James Lee Witt was interviewed by PBS Frontline very shortly after Brown resigned and asked the following: Q: You think he got a fair shake in this? JLW:… I think that he was dealt a bad hand in the sense of the leadership and the responsibility, and the resources [were] taken out of the agency to the extent that it made [it] difficult to lead. James Lee Witt had been hired by Louisiana a couple days after Katrina made landfall to come in and help the state - to include giving them classes on NIMS. Am I allowed to say that?

Anyway, you can tell JLW has a lot more criticism for Allbaugh, Brown's predecessor and "friend" who hired him and then skipped out when FEMA got rolled up under DHS.)
Big topic of FEMA getting rolled under DHS and stripping funding as well as removing Preparedness from FEMA and rolling it under a DHS Directorate, I would again recommend reading the full chapter on FEMA Preparedness in "A Failure of Initiative". (Probably wasting my breath here, but worth a try.)
When did Brown get appointed as PFO (Principal Federal Official) for Katrina? Look it up, it was August 30, 2005 at 9 PM. Tuesday evening.
Who was it before?
::

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Chertoff.
References:NRP Dec 2004, pages 3, 4, and 9;
HSPD-5; Management of Domestic Incidents
The Secretary of Homeland Security is the principal Federal official for domestic incident management.
Pursuant to HSPD-5, as the principal Federal official for domestic incident management the Secretary of Homeland Security declares Incidents of National Significance (in consultation with other departments and agencies as appropriate) and provides coordination for Federal operations and/or resources, establishes reporting requirements, and conducts ongoing communications with Federal, State, local, tribal, private-sector, and nongovernmental organizations to maintain situational awareness, analyze threats, assess national implications of threat and operational response activities, and coordinate potential or actual incidents.
HSPD-8 National Preparedness
The Secretary is the principal Federal official for coordinating the implementation of all-hazards preparedness in the United States.
The President appoints FCOs - which happened when emergencies were declared in the states, triggering the release of funds, which only FCOs can obligate; the DHS Secretary designates PFOs. When had a FEMA Director (used to be Director, now it's Administrator) been a PFO previously: never. When since: never. Brown was untrained and not on the PFO roster. But Chertoff flicked the booger very adeptly onto Brown.
The chain of responsibility for urban evacuation, highly debated after Katrina, was really quite simple, according to homeland-security mandates: the mayor; the New Orleans director of homeland security; the governor; the federal secretary of homeland security; the president.
Brinkley, the Great Deluge
I don't see FEMA Director in there at all.
So, yeah, Brown was not all that and a bag of chips, but he did perform ably in 2004 hurricane season. No, he was not cut out to be a PFO or even perform PFO duties, but there's a reason no FEMA Director or Administrator before or since has performed those duties - the position had only been written into the NRP by DHS for the 2004 NRP, and then was killed first by Congress through writing provisions into funding bills, then officially killed in 2010. It was a bad concept.
Why does Brown get the hate while Chertoff gets to slip past most discussions? (As I noted, he's only been mentioned once or twice in this thread and very much in passing.) My opinion is the reasons are: Bush praising Brown "heckuva job", and the revelations of stupid emails (and possibly the fact that he clearly resented being PFO, and defensiveness post-Katrina). If Chertoff had been publicly praised or any emails had surfaced, maybe it would be different. As it is, I would say Brown gets overly blamed and Chertoff gets largely a free pass for something that he was more culpable for.
Regarding the prepositioning, and magnitude of prepositioning; I will defer to one of the FEMA "bureaucrats" as Randfan likes to call them. (I would also recommend Scott Wells' testimony). The Katrina Lessons Learned excerpt does remind us that initially Katrina was projected to hit mid-panhandle Florida before moving to hit New Orleans, and some prepositioning occurred to have items closer to the Florida area.
Interview with Paulison, Director of the Federal Emergency Management Agency; acting director after Brown (September 2005); previously director of the Preparedness Division of the Emergency Preparedness and Response Directorate/FEMA in DHS 2003-2004; U.S. Fire Administrator December 2001-2003
FEMA had response plans and resources dedicated to this hurricane before it made landfall, resources which, based on previous experience, would have provided a good beginning to the response and recovery efforts. FEMA expected a Category 4 or 5 storm, so we had prepositioned a tremendous amount of equipment; hundreds of tractor-trailer loads of food, water, and ice; urban search and rescue teams; and disaster medical assistance teams (DMATs). This was a standard predeployment action for our agency, just as a fire department would preposition resources at a large sporting event in its jurisdiction. If the event goes well, you return the assets; if not, you are ready to respond quickly where you anticipate needing them. Because of initial reports of the potential size and scope of Katrina, FEMA had sent a considerable amount of supplies and manpower. As I look back at FEMA’s initial prepositioning of resources, it is clear we expected, in terms of need, what we’d see in normal level 4 or level 5 hurricanes. I say normal; however, clearly, they’re all somewhat different. The FEMA pre-event needs assessment was for a standard level 4 or 5 hurricane. That’s what the FEMA system expected to see.
I think what FEMA didn’t expect was the failure of the levees. The large and stranded population in the Superdome was a good example of a few of the things FEMA had not expected, ending up with 20,000 to 30,000 people in the Superdome (probably nobody will ever know the exact number) with no food, no water, and very little security. We did not expect the staggering number of people that showed up at the convention center. We did not expect to end up evacuating entire hospitals. We needed to assist thousands of patients, many of them invalids, from hospitals and nursing homes. That’s not what FEMA normally does, but we ended up in this role. We ended up doing air lifts, which we don’t normally get involved in.
The levees were a point of failure. Although we had preincident information that there was a probability of flooding, we had assumed that that would happen if a storm were to stall over the city of New Orleans. Failure of the levees was a possibility; however, we had assumed it would be the result of a stalled continuous downpour.
The resultant issues surrounding our need to organize the largest rescue efforts ever undertaken in our country stalled some of our other more routine efforts, as resources and manpower were shifted to rescue the trapped and stranded Americans in New Orleans. These efforts were further complicated by the lack of infrastructure and access, which prevented the immediate insertion of our ground-based forces. The geographic enormity of this event is also worth mentioning here: FEMA had an area of response of 90 square miles.
A Failure of Initiative said:
The Federal Emergency Management Agency (FEMA) positioned an unprecedented number of resources in affected areas prior to Katrina’s landfall. Indeed, FEMA’s efforts far exceeded any previous operation in the agency’s history. A staggering total of 11,322,000 liters of water, 18,960,000 pounds of ice, 5,997,312 meals ready to eat (MREs), and 17 truckloads of tarps were staged at various strategic locations in and near the Gulf region prior to Katrina’s landfall.1 FEMA also pre-positioned 18 disaster medical teams, medical supplies and equipment, and nine urban search and rescue task forces (US&R) and incident support teams.2 Rapid Needs Assessment Teams also were deployed to Louisiana on the Saturday before landfall.3 In Louisiana alone, on August 28, a total of 36 trucks of water (18,000 liters per truck) and 15 trucks of MREs (21,888 per truck) were pre-staged at Camp Beauregard.
Katrina Lessons Learned said:
In preparation for Florida landfall, FEMA delivered 100 truckloads of ice to staging areas in Georgia, and thirty-five truckloads of food and seventy trucks of water to Palmetto, Georgia. Also, anticipating a potential second Gulf Coast landfall, FEMA pre-staged over 400 truckloads of ice, more than 500 truckloads of water, and nearly 200 truckloads of food at logistics centers in Alabama, Louisiana, Georgia , Texas, and South Carolina. This was the beginning of the pre-staging efforts that increased to the largest pre-positioning of Federal assets in history by the time Hurricane Katrina made its second landfall on August 29, 2005
I realize some people want this to be as simple as a National Geographic picture, and a mission statement of "don't fail"

, but the whole picture is a little more complex. A Failure of Initiative is nearly 400 pages; A Nation Still Unprepared is nearly 800 pages; Brinkley's Great Deluge was 400-500 pages if I remember; the DHS OIG Report OIG 06-32 is nearly 200 pages - but hey, let's boil it down to bumper stickers. I've already said that I think sunmaster's order of blame is pretty accurate, with the inclusion of Chertoff.