I dig hole and put cages at its end with a chained dog bait for sieges. Bridges allow me free and safe access to surface, once whole siege is under ground.
I build underground entrance guarded with 2 chained dog at front, with room for depot and wall it all off from rest of my fortress with 2 rows of 3 cages to keep keas and other pest away. If this pest gets even through my 2 war dogs first, which does with kea happen from time to time. Dwarves until 0.44.05 clean only under ground, so it helps with cleaning blood pools too.
Despite all this I still create maximum military force. Militia mainly. Mostly for caves and fun. Now maybe for raids, if the bugs will be ironed out.
Militia with training schedule like 10-2-2-2-2-2-10-2-2-2-2-2 so I can use most of those Dwarves in their civilian professions.
I start my military from shields. Then I add weapons and then I allow them to train.
10 squads: 2 hammers, 1 mace, 2 swords, 1 light xbow, 1 heavy xbow, 1 pike, 2 battle axe.
Light bows using mainly (willow?) adamantine crossbows and it is formed from captain of the guards and consist of the most weakest Dwarves in my fortress.
Heavy bows using copper->silver (-> moded platinum) crossbows and it is formed from hunters. I provide 20 heavy bows for this squad use alone.
I let them train in barracks, though maybe it is a mistake to do so with Guards. They still train their archery, shields from there too.
I let them train in archery ranges providing as many bone bolts as possible. Oak bolts usually go for hunting. Reserving metal bolts for combat, but sneaky hunters steal those for hunting too. Grr...
The only down side is, that legendary military Dwarves start blinking in u-menu, even when turned into civilians. Most people using Dwarf Therapist for those things, so maybe not so important. Not like me. Vanilla client all the way!