Currently, the demon base was in a very lax state. Demon warriors patrolled everywhere, but they were mostly going through the motions rather than putting in any real effort.
Oh sure, some time during when they first invaded this world the weakling humans had tried to infiltrate their base to cull them, but the moment they entered their territory, they would suffer intense weaknesses.
After failing so many times, it had been eons since they tried again and most of the time, they were forced to defend themselves at their side of the battlefield, unable to have the luxury to creep over here. If it wasn't for those pesky, meddling cultivators, this world would have long fallen into their hands.