Elrond cautioned the Fellowship against taking oaths because he knew that they
were more binding than they knew. Such is the nature of oaths - Sauron's genius
was to divide and conquer; via the Palantir, via Saruman's plausibility, even
to his offer of free range through time & space to the Nazgul.
I always read those quasi-mediaeval oaths as echoed in more contemporary
marriage vows. An alliance of strengths, an acknowledgement of a common enemy
or shared purpose. Denthor's response was reassuring in the novel, despite
being an OTT headcase in the film. "I will not forget it, nor fail to reward
that which is given: fealty with love, valour with honour, oath-breaking with
vengeance".
OK, in real life, capriciousness is rewarded with love, valour with
redundancy, and oath-breaking with golden handshakes. However, Beregond never
regretted his oath, and saw clearly that Faramir, Denethor's heir, had
potential. If Denethor had been capable of alliances - or had seen them as
possibilities, rather than the prerogative of his King, he would have held his
own instead of coming under siege alone. It was not for nothing that the value
he placed on loyalty was the one thing his sons remembered about him.
Faramir. Merry dedciated his service to Thengol, and ended up trying to
disobey his command because it went against what he knew to be right.
Back to Feanor, the first oath taking, it is evident that his oath was folly
and led to the destruction of him, his people, and all that took oathes with
him.
