Not that simple although that is the usual response....it's for
more political than religious reasons. Henry VIII did it cos he
needed a male heir to ensure stability in his reign. If you have no
obvious heir, every nephew and cousin next in line will look for a
chance to do you in and take over the throne.
His first wife, Catherine of Aragon was a Spanish princess who
could not give him a son. He sought to annul the marriage (not
divorce) on the grounds that his marriage to her was not valid in
the first place. You see, Catherine of Aragon was actually married
to Henry VIII's brother, Arthur, who was the Prince of Wales.
Arthur died and so Catherine married Henry, who became the next
king.
But as you know, taking your brother's wife was prohibited in
Leviticus and so a dispensation from the Pope was necessary to
marry. Catherine's father, the king of Spain, exerted pressure on
the Pope and that dispensation (permission) was given although some
might dispute if that could ever be valid.
After the marriage, however, Catherine could not bear him a son.
Henry began to look at the texts of Leviticus which says that if a
man takes his brother's wife, they shall be childless. Although
they had a daughter, Mary, that didn't count in Henry's mind. The
King began to petition the Pope for an annulment. He apparently
thought that the earlier dispensation given was probably not valid,
that's the reason why he had no son..
Catherine objected to an annulment and she had influence in that
she was a princess of Spain, a powerful nation loyal to the Pope
and her nephew was the Holy Roman Emperor. Whilst the Pope was
deciding what to do for the next 6 years, the young Henry VIII made
his mistress, Ann Boleyn pregnant. Henry panicked. If Ann gave
birth to a son, he had to get that annulment before the baby is
out, or the child would be illegitimate.
Left without much of a choice with the Pope procrastinating and
Ann's belly growing, he rejected the power of the Pope in Rome and
set up the Anglican Church. The head of the new church, the
Archbishop of Canterbury, gave him the annulment.
Unfortunately for Henry, all that was for nothing. Ann Boleyn's
child was a daughter (the future Elizabeth I) and Henry remained
very much a Catholic in religious practice until his death.
