Māori invented trench warfare in the 1800s. Their fortifications were surrounded by palisades, and they dug trenches beneath, shooting hapless British soldiers from the gaps between the ground and the bottom of the wall.
The Romans were something else. I was reading about the period around the Illyrian uprising recently, and learned that at that time, standard practice for a legion was to build a massive fort, trenches and all, every night they camped.
It's pretty incredible (and often terrible) what humans with hand tools can do when sufficiently organized and motivated.
The basic concept of a trench with something like a wooden barrier proximate goes back to neolithic times. Interestingly most of these sites we've found seem to not be fortifications but rather something ceremonial. It's ambiguous.
Fra Giocondo (among others) would like a word with you:
> The second siege was that of Padua in 1509. A monk engineer named Fra Giocondo, trusted with the defence of the Venetian city, cut down the city's medieval wall and surrounded the city with a broad ditch that could be swept by flanking fire from gun ports set low in projections extending into the ditch. Finding that their cannon fire made little impression on these low ramparts, the French and allied besiegers made several bloody and fruitless assaults and then withdrew.
I expect that trench warfare is a natural side effect of enclosure trench systems used when taking a fortress. Obviously field fortifications are older than that, but I mean the variety that implies firearms and artillery.
There's a good video on this event, by [LindyBeige](https://www.youtube.com/watch?v=s6QhW5S8Gk4). Their videos are very informative and entertaining, but very focused on Britain.
