Second fall, right after the caravan and liaison show up, the dwarven village of bespokegears was jumped by a goblin ambush. With four huge squads of drowspider riding archers. Bespokegears' defenders numbered two novice marksdwarves in decent leather, two novice fighters in steel, two unarmored war badger dogs, and a war animated iron spear. Fortunately, a hall of weapon and cage traps stood between the dwarves and their attackers. Total losses on our side: two badger dogs. The spear has a name now, "Zust Tormentinghop." The four military dwarves all cowered underground staged a brave final defense in case the locked hatch failed to hold. Losses for the greenskins: sixteen giant drowspiders, five aim-fo-ya-throats, a war blood wolf, and a furious flagellant leader-type captured in a cage.
That was without a doubt the worst ambush I've ever encountered. Luckily everyone was inside taking stuff to the trade depot at the time. The lesson here seems to be, "Even if you find a spire right off the bat, don't mine candy like a madman and make 1.7M in created wealth before you have the dwarves to use it."