1. Why was there not a serious force waiting for the Company on the west side
of the bridge?
They assumed the Balrog was going to take care of business on the other
side.
2. How could this guard force not be fully alerted and ready for anything?
They were so convinced they were going to win that they got hammered in advance
of the actual victory ? Or maybe those flames exposed them to high
levels of carbon monoxide and carbon dioxide which dulled their
wits even more than usual.
3. Why in the WORLD didn’t the forces of evil concentrate on holding the exit,
instead of wandering around in a maze and getting cut off by their own fire?
If the forces of evil were truly competent our heroes wouldn't stand a chance.
4. In fact, since the orcs in the chamber of Mazarbul already knew about the
fire, how is it that they were cut off at all? There were all kinds of
connecting passages.
See #3. Perhaps the fire blocked some of their passages as well.
5. Is it possible that there aren’t really very many orcs in Moria, and that
they just don’t know the place well? And/or that the orc in black armor that
speared Frodo was the only high-initiative individual in the place?
I think it is quite likely that there were not many orcs in Moria. At
least on an orc per square feet basis. It's a big place and there don't
seem to be that many possibilities for decent raiding in the area with
Lothlorien and it's elven archers nearby.
CHALLENGE
What do you suppose Sauron heard about this entire encounter (Balrog and all),
and what did he think about it?
Sauron: "That Gorghâsh always was a third-rate flame of
Udûn. Defeated by a second rate Maiar without his staff.
..*grumble* Why is it so difficult to get good help these days
?
"
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We who still labour by the cromlech on the shore,
The grey cairn on the hill, when day sinks drowned in dew,
Being weary of the world's empires, bow down to you,
Master of the still stars and the flaming door. --W.B. Yeats