> So, would it be fair to say that in nature Herlið refers to more

an agressor people and Fyrð as a protector/defender type of people?
(or am I misunderstanding here).

I think 'herlið' is just a neutral word for "troops", whatever they
may be used for. It can be used of invading soldiers, as for example
the army of the Huns in Hervarar saga ok Heiðreks, but also for
defenders or simply troops in general, as in the following quotes.
The first is from Ólafs saga Tryggvasonar in Heimskringla, followed by
an example from Völsunga saga:

Valdimar konungur setti hann höfðingja yfir herlið það er hann sendi
til að verja land sitt.
"King Vladimir appointed him as commander over the troops that he sent
to defend his land."

Atli konungur sendir mig hingað og vildi að þið sæktuð hann heim með
miklum sóma og þægjuð af honum mikinn sóma, hjálma og skjöldu, sverð
og brynjur, gull og góð klæði, herlið og hesta og mikið lén,
"King Atli sends me hither and wishes that you come to visit him in
great honour and receive from him great honour/respect, helmets and
shields, swords and coats of mail, gold and fine clothes, troops and
horses and great gifts."

I'm not sure about this 'fyrð'. There is an Old English word 'fierd'
or 'fyrd' which I think referred to a defensive militia. There is an
Old Norse word 'fyrðar' "men, warriors". I would have thought the
nominative singular would be *fyrðir, if it did occur (just my guess),
but as far as I know the word is only attested in the plural. The
dictionaries and glossaries that I've been able to consult give the
plural form only. As for usage, it's not a word that would normally
be used in prose, but part of the special poetic vocabulary. The
meaning seems to be fairly broad. It can refer to men engaged in any
sort of activity, or no activity in particular (e.g. when used as a
base word in kennings). It's true that Skáldskaparmál, part of
Snorri's Edda, a 13th century manual for poets, does contain the
statement 'fyrðar ok firar ok verar eru landvarnarmenn' "fyrdar and
firar and verar are men who defend a country", but this idea may be
inspired by certain similar-sounding words (e.g. an association with
words such as 'forða' "to save", 'verja' "to defend"); the whole
section explains the origins of such terms using folk etymologies and
perceived connections with mythological or legendary figures to
explain the words. In practice, as far as I know, they're are all
used in poetry for men in the most general sense. 'firar' is another
poetic word for men. A related word is used in the same way in Old
English and Old Saxon poetry. I've seen 'firar' explained by modern
scholars as being related to words such as ON 'fjör' "life", OE
'feorh' "life", Gothic 'fairhvus' "world"; compare also OE 'ferhþ'
"mind, heart, spirit, understanding; life". Not that a words origins
dictates how it is used at any particular time... The singular of
'verar', 'verr' occurs in prose with the meaning "husband".

> > Also the word Lith, I have seen used to refer to warbands, but I

cannot find any information on 'lith' - is lith the same as lið?

Presumably 'lith' is just an Anglicised spelling of the Old Norse /
Icelandic word 'lið' which is used like 'herlið' to mean "troops",
"soldiers", "forces", "an army" (besides having various other
meanings). Are these links any use?

A Modern Icelandic dictionary:
http://digicoll.library.wisc.edu/cgi-bin/IcelOnline/IcelOnline.TEId-idx?type=header&id=IcelOnline.IEOrd

Some Old Norse / Icelandic dictionaries:
http://norse.ulver.com/ondict/zoega/index.html
http://www.ling.upenn.edu/~kurisuto/germanic/oi_cleasbyvigfusson_about.html#images

The first, Zoega's, is actually an abridgement of the other.

> Also, how do I pronounce these words, Herlið and Fyrðar?

In English, however you like! In Icelandic, hmmm... The letter 'ð'
is like 'th' in English 'heather'. The 'r' is rolled or trilled, more
or less as in Scottish English, or Spanish. All Icelandic words are
stressed on the first syllable. 'herlið' as a compound word also has
a secondary stress on the second syllable, like two-syllable English
compound words, e.g. 'headline', 'catflap', etc. The vowels, 'e' as
in English 'bed'. 'a' something like the 'a' in English 'father'.

Modern Icelandic: 'y' like 'i' in English 'pin'. The 'i' in
'(her)lið' as in English 'pin', but longer in this word.

Old Icelandic (early medieval), probably, to the best of my knowledge:
'i' short and tense as in French 'dix'. 'y' like French 'u' in 'lune'.

Hope that wasn't completely baffling. I would just add that I'm not a
native speaker of Icelandic, and that my understanding of the
language, ancient and modern, is far from complete! Also that it
isn't really possible to explain with perfect accuracy the sounds of
one language in terms of the spelling of another.

Llama Nom