And those heavy equipment like artillery and tanks, which were already few in number, inevitably suffer losses during deployment. Without a proper logistical supply and without ample time for repairs and maintenance... mostly, they will have to be abandoned halfway, wasted during the back-and-forth process.
Valuable and dwindling combat power is consumed in meaningless comings and goings. I assume the Dorne side generals must feel quite distressed. But there's nothing they can do, because the Laines Empire can no longer be relied upon.
If they don't retreat in time, and once the Laines Empire unilaterally makes peace with the Great Tang Empire and chooses to surrender... their situation will become even more difficult. By then, cooperating with Laines Empire's railway system won't be as easy as now; they might not even find a proper train.
