What is impossible for us is accomplished by God with ease, said K. Sambandan, in a discourse. We have many examples that show this.
In the Kamba Ramayana, the poet shows how easily Lord Rama broke the bow that no one else could even move. He lifted it as if it were a garland of flowers. People saw the bow and the next thing they knew it was broken. All they heard was the sound of the breaking. So quick was the act of breaking. Between the act of picking up and the act of breaking the bow, there was hardly any significant gap in time.
Lord Siva, likewise, destroyed the cities of three demons in a second. The bhuta ganas were proud of the fact that they were accompanying Him and they began to see themselves as indispensable in the battle that they expected would follow. Lord Siva decided that the bhuta ganas must be taught a lesson. So all He did was smile at the three cities, and His smile was the agent of destruction. With just a smile, He destroyed the three cities, burning them down completely. Thus He totally dispensed with the service of the bhuta ganas and even the use of any kind of weapon. His smile became His preferred weapon, showing that He is independent of anyone, and needs no one’s help to accomplish anything.
In his Tiruvachagam, Manickavachagar says that to Lord Siva even the arrow became unnecessary. Thus we can infer that He eschewed the use of weapons in His destruction of the cities of the three demons. These stories are all intended to show us that to Him all things are possible, and He needs no one’s assistance to accomplish a task.