The phallic stage, from three to five years old was the
stage where the child's sexual identification was established.
During this stage Freud hypothesised that a young boy would
experience what he called the Oedipus complex. This would provide
the child with highly disturbing conflicts, which had to be
resolved by the child identifying with the same-sexed parent.
Freud thought that, during the phallic stage, the young boy
develops an intense sexual love for his mother. Because of this, he
sees his father as a rival, and wants to get rid of him. The
father, however, is far bigger and more powerful than the young
boy, and so the child develops a fear that, seeing him as a rival,
his father will castrate him. Because it is impossible to live with
the continual castration-threat anxiety provided by this conflict,
the young boy develops a mechanism for coping with it, using a
defence mechanism known as 'identification with the aggressor'. He
stresses all the ways that he is similar to his father, adopting
his father's attitudes, mannerisms and actions, feeling that if his
father sees him as similar, he will not feel hostile towards
him.
http://www.holah.karoo.net/freudstudy.htm