When the time came for the transfer of lands, Spain's daughter and son-in-law went to the Duchy of Parma.  They found it to be ruled by French troops.  Napoleon had not kept his part of the deal.  Spain was signing secret treaties and not being fair either.  Spain was delaying things for as long as possible and Napoleon was becoming very upset.  He decided the French must take Louisiana back by force.  France feels they can not be friends with the New America because it seems too much like England.  They want the Louisiana so the new country cannot grow.