Somthing I did not mention earlier is that straw bales are bullet proof. Therefore they would make good defensive barriers if found in the countryside. If sprayed with water or pyecrete in freezing weather they would be even stronger. If not, then they would be portable and could be trucked to new locations as front lines change. In the far north, they are even used as flooring in buildings to prevent melting permafrost and sinking into it. Should work for frozen mud too, preventing it from thawing under a strawbale building or even a military tent.