I got a bit confused about these two phrases, or more precisely, the latter.
Fighting against sb/sth always means - well, fighting against.
But then, if A fights with B; isn't it ambigous? Doesn't it mean that A & B can be either allies or enemies (depending on the context)?
I checked two dictionaries but it still left me in doubt.
What I guess is that "fighting with" equals "fighting against" when referred to individuals (say, boxer X will fight with Y, or someone's parents are "fighting with eachother"), while in case of countries, armies etc., it indicates an allied struggle (as in "Italians fight with Napoleon... against Austria").
Please correct me (or confirm what I think) :)
But not always.
Any other answers??
Here's my take on it.
I think you're pretty spot on in your analysis.
"fight with" can mean by along someone (fight together).
Here's an example from the Cambridge Dictionary:
They fought with (= on the side of) the North against the South.
I would add that you fight with someone, but that you fight against something (an idea, a concept)
Here's another example:
"He fought against racism."
The previous example is also from the dictionary.
It would be incorrect to say: He fought with racism.
I googled "fought with racism" and nothing came up.
I'm wondering about something though.
Take the following examples:
#1. "He fought with alcoholism all his life."
#2. "He fought against alcoholism all his life."
#1 would mean he struggled with alcholism all his life.
#2 would mean that he fought against alcoholism all his life (without necessarily being involved in it.)
So I would add that you fight with when there is some kind of involvement and that you fight against when you are not necessarily involved with what you are fighting.