Slavery in the european 15th century?

[Hakan Hugosson]

Dear all,

I'm reading a book on Venetian history (A History of Venice, by John 
Julius Norwich), and in it is mentioned that rumour had it that a 
Venetian doge (Pietro Mocenigo), who died in February 1476, did so 
because of the attentions of the 10 turkish slave girls he kept as 
concubines.

So my question is to what extent were slaves kept in the european 15th 
century? I guess the regional differences are enormous, and one needs 
some definition of slavery (working for no pay against one's will?), but 
I have very little insight into the history of slavery so any and all 
information is, as usual, welcome. Prisoners of war used as slaves, etc.?

As far as I know slavery was forbidden in for example Sweden 1335, but 
for other countries I don't know, slavery was generally abolished by 
European countries in the 19th century as far as I know . Differences 
between christian and non-christians held as slaves? Slaves are for 
example archetypically used for galley rowing, but my book also mentions 
that from the begining (in Venice - it later changed, but when?) rowing 
the galleys was done by highly paid and trained soldiers - who also 
joined in the fighting. I also remember an article on slavery attempting 
to total the slave trade over time and here a great number of slaves had 
european destinations.

Just a small aside that someone might help clear up for me,

Yours,
   /haakan