No, it wasn't. In fact, I remember specifically that the GTA and the PVN were still seperate entitities during Silent Threat, and that the entire thing was a rebellion by the GTA's Intelligence Division - NOT the SOC, which is what the GTVA uses.
Also, as an off-topic note: Having read through the various seperate descriptions of the GTVA's formation, it's struck me that the controlling entity in the GTVA is actually the Vasudans, not the Terrans, as we are generally led to believe. If you read it, it seems that the Vasudans come out of the Great War better than ever, while the Terrans are fractured and only unite when the GTVA is formed.