Why did the Austrian army surrender at Ulm so quickly?

General Questions
#1

Based on my viewing of War & Peace, the Austrian army of the 3rd coalition, under General Mack, was surrounded at Ulm and then surrendered.

But why was he surrounded? Why didn’t he move his army back? And if surrounded, why not fight through (if insufficient supplies)? Or hold out there for the Russian and other 3rd coalition forces to arrive, which were on the march?

It seems like the history books give me the conclusion that there wasn’t much fighting, which seems strange to surrender so quickly without more bloodshed.

#2

Though you do seem to have a dislike for wiki cites ;), the one for the Ulm Campaign ( i.e. not the battle ) offers a fair degree of detail. There was in fact plenty of fighting prior to the final action at Ulm, by which point demoralized and doomed Austrian troops were indeed surrendering in droves after only minor contact. For example the battles of Wertingen, Gunzburg, Haslach-Jungingen and Elchingen.

Basically against better advice Mack advanced too far west, then reacted sluggishly when he found he was in danger of being comprehensively flanked by a far stronger army. When he finally made various spastic moves to attack or break out he was consistently stymied. Meanwhile he was bleeding deserters and soon found himself low on supplies and morale. Basically his position just crumbled away as various heavily outnumbered outlying commands were ground up piecemeal, his commanders surrendering one by one while he dithered in the city. At the final moment he was besieged and basically would have not been able to hold out long, so he negotiated a surrender.

#3

Ok, I only looked at the “Battle of Ulm” page, one which had not the same level of detail as the Campaign.