The speed of the fire can be suprising. The fastest I have seen personaly covered a measured mile of road in just under 1 minute, making something better than 60 miles an hour, in the crowns of a pine plantation. One of the problems we face is that the intense heat carries leaves from the eucalypts high into the air and drops them still alight or smouldering well ahead of the fire. I have been burned by leaves droping at least 15 miles ahead of fires, and they start multiple new fires well ahead of the main blaze, giving the impresion that the fire you were watching in the distance is suddenly upon you.

When I was in the army one of the things that caused a lot of disatisfaction at the digger level (troops) was the failure of the authorities to use us for disasters such as this. That problem related to our system of government, where the fire fighting authority needed to aproach the state government, who discussed it then went to the federal government, who discussed it and went to the army, who determined what they could do and reported back to the feds, who discussed it and made an offer to the state, who discussed it and took the offer back to the firefighting agency, which accepted or asked for something else, and the processs went back and forth repeatedly.
Our constitution was developed by governments for governments, and aimed to protect the rights of the various levels of government under the comonwealth model, and we have nothing like the US FEMA who can take control.
Seing the speed with which troops and equipment were deployed this time makes me hope a change is in the air.

In some past fires we have also seen some petty public service empire builders try to do it alone, without seeking help until it is too late, but hopefully those days are gone.