I routinely consolidate 75 to 80% of all of my units in a single formation during the first 24 to 48 hours of the game, with 12 or 13 infantry regiments spear-headed by a couple of armored car brigades. Numerical superiority and light armor support are just about the only advantages available during the first two days until you produce some light tanks and artillery. That said, you are still going to suffer some casualties even when you have a 12:1 or better numerical advantage, and you will typically lose one infantry unit for every two or three enemy infantry regiments you kill.
I am unaware of any strategy for "ghost-riding" through an entire country during the first few days and suffering zero casualties and zero unit losses. If someone knows how to do this, I would sure like to hear about it.
