What was the primary reason that the Cicones were able to do such damage to Odysseus€˜s men?

In Book IX of the
Odyssey,
Odysseus sacks Ismara, the city of the Cicones, kills the men and
enslaves
the women. He then wants to move on immediately, but his men disobey him and remain
in
Ismara, drinking and feasting. They are soon attacked by other Cicones who
live further inland.
These men are better warriors, stronger,
better-equipped, and more numerous than those they had
just
defeated.

As well as being more numerous, the Cicones take advantage
of
the element of surprise in attacking the Ithacans. They know the terrain
and are fighting for
their native land. Odysseuss men have just been eating
and drinking immoderately and are in no
condition to join battle. The Cicones
therefore defeat them easily, killing six men for each of
Odysseuss ships.
Odysseus stresses the greater numbers of the Cicones as the primary reason
for
their victory, while mentioning the other factors in
passing.