Just tried this and...argh!
Orcish machinegunners.
We can't withstand firepower of that magnitude!
Made a new fort in a nice new spot. Winter in the first year rolled around and a small group of orcs appeared and laid siege to my 7. Tough fight, won in the end but took 3 nasty red wounded dwarves and that was after the orcs waltzed through a few stone traps.
Fair enough.
Summer of the next year arrives. The elves never actually got any trading done as a herd of skeletal elk scared them off before they arrived at my depot, and I 'd not had much to trade witht he dwarves last autumn. Luckily I didn't need much either and in mid summer a huge horde of migrants showed up
2 weeks later, so did a huge horde of orcs. Lots of crushers and seemed to be lead by 2 "elite snipers", aka wandering minigunners. Between them their arrows blotted out the sun, which was bad as my dwarves were not cave adapted and the arrows were coming towards them. They all died.
It was sort of like this, only with a pair of bow wielding orcs instead.
http://www.youtube.com/watch?v=jI42TeuwlMw
I never had any real trouble, apart from dwarfs going insane and murdering 2 of my champions...
I have been sieged by Orcs probably around 4-8 times... the last one had about 40 or 50 units. But I have a tower built on a hill and the only way onto the hill is on a drawbridge (hill surrounded by walls) and once you past the draw bridge and 10 cage traps and 8 weapon traps there is a tower with the stairs inside and I put my almost champion crossbowmen up there.
But since I have 4 other goblin races and for some reason they like me even though I steal all ofd their stuff... and I get caravans what seems like every 10 minutes, so they usually take care of all goblin sieges (makes me mad) but the current orc siege took care of the caravan.
Make sure to start training wrestlers right away so you can have legendary guys very fast, and of course make a good defendable entrance right away, then you basiaclly can almost not lose from sieges.
And make a ton of cages so you can have arena battles... I can't wait to see how my captured dwarf (enemy one) does against 1 orc... if he wins he is against 2 orcs... and finally 3. IF he wins I will set him free... although he will probably run back and get killed. And I got a few goblins... and a room with wooden spikes.