Soldiers sneak into enemy land. Then they have not to be sniffed by enemy. If it do well, they can atack enemy supply base, headquoter, access road, other enemy soldiers etc,,,. Fnally enemy front line would isolate.
Also, if enemy found sneaked soldiers, enemy bomber and aritilleryman can't attack them because the area which enemy wants to attack is their land. Enemy bombardment would kill friends.
Once soldiers sneaked into our territory, attacking them is difficult. When we found them, at least several our facility was gone. But they have weakpoints. First, they are not able to suppliy foods and ammo. Second, sneaked soldiers are not able to supported by friends. That is to say, they will isolate.
In middle of WW1, Russian soldier " Brusilov " created Infiltration tactics. In WW2, Japanese Army was good at this. For example, in Battle of Singapore, Japanese tank "Type97 CHIHA" and "Type 95 HAGO" conducted "Infiltration tactics" in the middle of night. Basically, tank is used in the daytime, so British soldiers were surprised at this because Japanese tanks appeared at night; in British military territory!
Type95 HAGO
Type97 CHIHA