Ya, they started it!
As for our alliance being able to steamroll anyone, I wouldn't say that. Ever since the war ended, all France's been doing was build troops ad nauseum. I think France wants revenge for the unilateral defeat they suffered in WW1, and I'm pretty sure the second war will be a lot more dogged than the first one. And we won't have to wait long for it, either.
The first war was a beauty though. Here's a quick rundown:
===The road to war===
Austria DoWs 2 Sicilies, to whom Spain is guaranteeing independence. Russia and Spain seize the opportunity for a war without a prestige loss and jump in. Prussia pledges support should it be needed as Prussian armies redeploy along the French and Austrian border. France dishonors her alliance with Austria, deploys troops on Prussian and Spanish borders and assures Prussia she won't invade. Faced with an overwhelming Russian invasion and no allies, Austria quickly ends the war by taking white peace with 2 Sicilies.
===The flames of war===
Immediately after the war, Russia signals to her allies that the time to go after France is now. Prussia and Spain, already massed on the French borders, agree and join the war as Russia DoWs France. France, left with no friends after having dishonored her alliance and unprepared as she had her strike at Prussia pre-empted (a French assurance of neutrality should be, and was, taken as a declaration of war in Berlin, given the past diplomatic history of the French player) valiantly fights against the Prussian and Spanish armies.
France claims to have "held off" the attack for 6 months - of course, at the end of these 6 months the front lines moved from Alsace-Lorraine and the Pyrennees to southern France and French north Africa being in Spanish hands, Paris in Prussian hands along with a large swath of territory leading up to it.
War in the west, beginning
War in the west, middle
War in the west, after 6 months
This is where the war got interesting, as France deployed its last 9 divisions around Paris, got a military tech infusion from the USA and got Austria/OE to board its sinking ship. The result of this intervention was really to give Russian troops some much-needed exercise. The bear was, until now, largely idle other than protecting Prussia's northern flank by blockading the entrance to the Baltic. Once the other two joined the war, not much fighting occured on the Austro-Prussian front. Austria and OE were too busy getting steamrolled by Yogi to care about much else.
===The aftermath of war===
Austria and the OE's decision to jump onto the sinking ship ended with Galizien ceded to Russia by Austria, Armenia ceded by the OE, while France was forced to cede the iron province of Alsace-Lorraine (giving Prussia easier access to Paris next time) and Zurich, while ceding one more province back to the Swiss. She also gave up the western third of its north African territory to Spain, including an iron province.
Here's my rough guess at the size of the forces mobilized:
===========================================
Prussia: 850,000
Russia: 800,000
Spain: 150,000
Austria: 350,000
France: 550,000
Ottoman Empire: 400,000
Total (estimated): 3,100,000
The number isn't staggering, but it's not a small war either, especially considering I'm not counting the AI (Netherlands, UK) and that this happened only 15 years after the game's start.
The good guys won this time. Alliance gains are outlined in green, not counting Armenia that the OE ceded to Russia.