And the U.N.'s envoy to Syria was right.
Getting the Americans, the Russians and most of all the Saudis and the Iranians into the same room to search for solutions was a major diplomatic feat.
The fact that the talks did not collapse and that the players are meeting again this weekend is even more remarkable.
It is one of the most serious and intense diplomatic efforts to try and end this horrible conflict.
But it could all fall apart if the sides are not willing to make major concessions and some very tough decisions.
1. Who represents the opposition?
One of the major weaknesses of the first Vienna meeting was that there were no Syrians at the conference to end the civil war in their country.
One reason: It is still unclear who would represent the opposition.
The spokeswoman for Russia's foreign ministry, Maria Zakharova, recently told Reuters: "The first (task) is to systematize and understand who we should consider terrorists in Syria and in the region, and the second is to establish a list of the representative Syrian opposition that can conduct negotiations with Damascus."
The Russians consider most groups fighting against the Syrian regime to be terrorists, but have said they would be willing to work with parts of the Free Syrian Army.
The U.S. and its allies have been working with the Syrian National Coalition as the main political body representing the opposition but it's not clear how much sway this group of exiles holds with armed groups combatting Assad on the ground in Syria.
The U.S. has also been aiding various moderate rebel groups. It will be key to find strong and credible figures representing the opposition if any sort of final agreement is going to stick.
2. Assad's future
At the last Vienna meeting, Secretary of State John Kerry said the U.S. "agrees to disagree" with Russia and Iran over the fate of Syria's President Bashar al-Assad, but added, "... we can't allow that disagreement to get in the way of diplomacy."
Excluding the future of Syria's president in the diplomatic effort may work for a while, but it will need to be addressed -- and soon -- as it is the main factor dividing the U.S., France, the UK, Saudi Arabia and Turkey on one side and Russia and Iran on the other.
The Saudis and the Turks want assurances that that Assad will relinquish power, while the Russians and the Iranians fear that the Syrian state will collapse if that happens. In the end, all sides will have to make concessions on this issue, otherwise the talks will hit deadlock and could easily fail altogether.
And while the issue of Syria's president is divisive among the nations meeting in Vienna, it is decisive among the adversaries in Syria.
Khaled Khodja of the main opposition group, the SNC has ruled out any participation in a peace process unless it is clear that Assad will leave. Meanwhile a top Syrian diplomat recently told me it would be impossible to keep Syria's state institutions from falling apart if the president were to leave office.
This is the toughest and most important problem to overcome.
3. Destroying ISIS
This fighters and armies active in Syria are more likely to decide this point than those meeting in Vienna, but important coordination must be agreed upon to make the fight against ISIS more effective.
Both sides -- the Russians, Iranians and the Syrian government on the one and the U.S. and its allies on the other side -- can boast of considerable achievements since the last meeting.
Syrian government forces -- with the help of Russian air and Iranians man power -- broke through the ISIS siege of the strategic Kweiris air base this week.
It was also a major morale boost for the Syrian army after a flurry of setbacks in 2015, and indicated that the Russian air force -- at least in part -- is also bombing ISIS targets.
Meanwhile, the U.S. and its Kurdish allies are increasingly degrading ISIS on the battlefield's Western front. Kurdish forces backed by intense coalition air support tried Thursday to liberate the northern town of Sinjar in Iraq from the group.
Both sides will need to coordinate their efforts more to defeat them and take the threat of a complete ISIS takeover of Syria out of the equation.
4. Iran and Saudi Arabia
Photos from inside the meeting room at the last Vienna summit showed Iran's Foreign Minister
Javad Zarif and Saudi Arabia's chief diplomat Adel Al Jubeir sitting as far away from each other as the room would permit.
But the mere fact that they were in the same room was a major achievement. Analysts have long pointed out that the Syrian conflict will not be solved unless both the Saudis and the Iranians are involved.
The two sides didn't exactly warm up to each other: The Iranians left it until the very last minute to confirm whether they attend the next round of talks because they felt they were being disrespected by the Saudis.
One of the major issues fueling Syria's civil war is the battle between Saudi Arabia and Iran for influence in the Middle East. These two countries will have to set those differences aside, at least for a while, if the Vienna process is to succeed.
5. Keeping the momentum
The first Vienna meeting left many questions unanswered, but there was a surprising amount of agreement between the parties involved, which was reflected in the final communique.
They agreed to task the U.N. with attempting to broker a nationwide ceasefire.
The parties agreed that Syria's political and social institutions must be preserved as well as Syria's territorial integrity and its status as a secular state.
Progress is needed on all these points quickly -- and it can only happen if the countries negotiating in Vienna manage to bring Syrians into the mix as fast as possible.
Otherwise, the diplomatic momentum that led to the first truly inclusive international effort to end the bloodbath in Syria could be squandered -- and Syrian civilians will be the ones to pay the price.