Both Pope John Paul II and Cardinal Ratzinger publicly stated their opposition to the US invasion of Iraq in 2003. As late as March 16, 2003 Pope John Paul II reiterated his opposition to the war in his Angelus address.
That is why, in the face of the tremendous consequences that an international military operation would have for the population of Iraq and for the balance of the Middle East region, already sorely tried, and for the extremisms that could stem from it, I say to all: There is still time to negotiate; there is still room for peace, it is never too late to come to an understanding and to continue discussions.
The war began two days later. In an April 2003 interview in 30 Days Cardinal Ratzinger expanded upon the pope's thoughts.
The Pope has very clearly expressed his thoughts, not only as the thoughts of an individual, but as the thoughts of a man of conscience occupying the highest functions in the Catholic Church. Of course, he has not imposed this position as a doctrine of the Church, but as the appeal of a conscience enlightened by the faith. This judgment of the Holy Father is convincing from a rational point of view also: reasons sufficient for unleashing a war against Iraq did not exist. First of all it was clear from the very beginning that proportion between the possible positive consequences and the sure negative effect of the conflict was not guaranteed. On the contrary, it seems clear that the negative consequences will be greater than anything positive that might be obtained. Without considering then that we must begin asking ourselves whether as things stand, with new weapons that cause destruction that goes well beyond the groups involved in the fight, it is still licit to allow that a “just war” might exist.
Why are we deporting a conscientious objector to the Iraq war and welcoming al-Qaeda sympathizers who would send their 15 year old child to fight in Afghanistan?