The First Vatican Council was held under a true Pope, Pope Pius IX in1869. Pope Piux IX was a true pope and very anti-liberal. Vatican I was a doctrinal council like all councils and it didn't contain heresies. The Second Vatican Council was called a "pastoral" council. It didn't define any dogmas. It was held under an antipope, John XXIII (Roncalli) as well as the next anti-pope Paul VI. Roncalli was rumored to be a mason. He was very popular with the press. Ask anyone who grew up in the 50s and they will remember hearing about "Good Pope John". Well, he was a "Good Pope" for the enemies because he was like them, a liberal. He opened the Vatican II council. The Vatican II Council has major errors and heresies that laid the ground for a new religion that Catholic across the world were tricked into. So, yes it had substantial changes. See here: http://holyromancatholicchurch.org/heresies.html Here is another interesting article: http://www.catholicapologetics.info/modernproblems/vatican2/renew2.html One the major problems today among traditional Catholics is what position to take among this crisis. There are those who take the position of sedevacantism and those who don't like the recognize and resist groups (sspx) and the conservative groups (fssp and novus ordo). The R&R and conservative novus ordo groups seem to think they can be in communion with heretics aka the impostor pope, bishops, and priests who occupy 99.9999% of all Catholic Churches today. The holyromacatholichcurch.org link I posted is from John Lane who is a sedevacantist. The catholicapologetics.info site is run by sspx type people.