(maybe that's not a good choice for Caesar,the tide certainly did not wait for him, at least in Britain)....

I know, PA, their feats are amazing - but Alesia stays in my mind, as do others particular to Caesar, because of the relatively short time they took to complete, under pressure of war. Hadrian's Wall took - ? - decades, so did building the limes in Germania, but when you've a half-million Gauls hot on your trail, it's something to show the kind of focus that developed Alesia, among other of Caesar's great engineering feats.

What always puzzles me - is it simply that we don't HAVE another general whose memoirs have survived, to compare the Roman army in the time of Marius and in the time of Caesar? Were its skills as finely-tuned then? Sometimes it seems to me that Caesar's engineers, like Vitruvius, just sprang full-blown from his own command center, and I know that cannot be true.