I don't think we really know what the Soviet strategy was. I suspect it varied over time. Certainly there's enough in the public record to support whatever position an analyst finds convenient.
Actually, we know quite a bit and it's quite transparent that the Soviets never bought into the idea of limited nuclear war. For them, if there was going to be a nuclear exchange it was always going to go all the way so there was no point in holding back. They did develop some plans involving limited nuclear war, mainly tactical use in support of the ground forces (see below), but from everything I have heard Soviet generals never took the idea of a limited nuclear conflict seriously.
It's interesting to note that there
was a big shift in Soviet nuclear thinking around the middle of the Cold War, but it resolved more around how soon nuclear weapons would be introduced into the conflict then how widespread the conflict would be. During the 50's and 60's, the Soviet military figured that nukes were just Very Big Bombs and that the war would start with a total nuclear exchange from the outset. They did not believe that the nuclear exchange by itself would be decisive and that the war would continue as a conventional conflict once the warheads were exhausted. Hence, a lot of their warplans involved the Soviet's using their nuclear warheads with the goal of facilitating the following ground war as much as hitting strategic targets.
Over the course of the 60's, however, the realization apparently set in among the Soviet military that a total nuclear exchange was not something that could be so easily brushed off. As a result, the 70's and 80's saw the development of a number of war plans which generally tried to keep a purely conventional conflict and avoid the nuclear stage altogether. You can see this in the Soviets promise to "no first-use" although their definition of that term does not consider a pre-emptive strike to be "first-use".
Some of the old thinking did persist though, hence the existence of the infamous "
Seven Days to the River Rhine" plan.
Something I do need to emphasize though: although the Soviets did ultimately wind-up drawing a unofficial line between conventional war and nuclear war, they always regarded it as entirely artificial one. As far as Soviet doctrine was officially concerned, there was no such thing as "conventional war", "limited nuclear war", and "total nuclear war". There was either war or there was peace. Nothing more, nothing less.