That's what the Shadows and Vorlons of c. 2258-2261 say, as does Lorien. But I'd like to know why/when they started being more proactive in enforcing their philosophies on the younger races. I mean was it as simple as "Starting a war just to honk off your neighbours" or did the 2 Old Races just stop trying to work things out with each other?
Well, until Mongoose produce something that contradicts it (and I really hope they don't and embrace what Matt Plonski wrote), the AoG "Wars of the Ancients" pretty much covers all of this.
The Kirishiac Lords (the ancients in the asteroid type ship) were the last race to attain First One status - that is developing manipulation of hyperspace for themselves which (unaided) takes millions of years of evolution and development. Until that point, as real space FTL isn't practical in the B5 universe, races did not get out and about.
Unfortunately, the other Ancients hadn't notice this happen (who mainly kept themselves to themselves and gave each other wide berths) until the Kirishiac starting rampaging through the galaxy and attacking all the other ancients and generally making a pain of themselves. It took a gruding alliance of the ancients (including the Shadows, sort of) to bring them to heel and show them the error of their ways (basically the most developed of the ancients short of Lorien, the Triad, demonstrated exactly what they could do to the Kirishiac if the were so inclined and the Kirishiac capitulated). The Ancients then resolved that a closer eye should be kept on the developing races so that they wouldn't get suprised like that again. Lorien was happy to see the races he had nurtured willing to take on a similar role.
Unfortunately the Vorlons and Shadows couldn't agree on a method of naturing and both went their own way at this point, whilst the others were content to just observe.
Unilaterally, the Vorlons decided that rather than keep every developing race under direct observation and hoping that they would naturally cooperate when they met races of similar development to themselves, the best bet was to let them loose in the galaxy before they would naturally develop this technology themselves (and hence be a threat to the other Ancients) by letting them "discover" a large pre-established jump gate network with easily copiable technology that (whilst they wouldn't understand all the underlying principles) build themselves. This way they would know they aren't the biggest fish in the pond (like the Kirishiac had thought) and natural racial arrogance would be kept in check - or at least it would if the Shadows weren't stirring the pot...
Lorien was deeply disappointed and retreated to Za'Ha'Dum until such a time as the two races could see past their philosphies. This was several million years ago, and the Shadows moved to Z'Ha'Dum to be near Lorien, whose blessing was very important to them, but of course all communication was rebuffed.
From there on in, the Vorlons and Shadows escalated their methods until we got where we are in 2261. But fundementally, it was about who had the "right" method of nurturing the younger races, whereas of course it should have been about responsibilities...