Judging from the news, the enemy indeed had no suspicion that the citizens of the city were behind it. The last message left by Li Sanyuan was about dealing with external threats to his city.
Subsequently, he set off with his elite forces, leaving behind in the city signs of battle that have been obliterated over time and their traces erased.
The skeletons he summoned would automatically vanish when their time was up, leaving nothing behind.
There might be some residual energy for a short while, but it would eventually fade away.
As for the remnants of the ground combat armor they later excavated, nothing discernible was left as the remains were heavily damaged.
Experts could only guess that the enemy had heavy machinery or large creatures capable of causing such damage. There were also signs of fire, suggesting the presence of a fire mage among the enemy ranks.