A Twitter post from Akatsuki Natsume confirmed that “Combatants Will Be Dispatched” was already scripted before Konosuba was aired; only he was hiding it until his close friend ratted him out to the Sneakers.
Natsume Akatsuki, the author of Konosuba and Tappei Nagatsuki, the author of Re:Zero are close friends. In fact, they came up with their successful titles in a bar while discussing Isekai ideas they liked. Some of the ideas included a character wearing a swimsuit who is incapable of doing anything, and a story in which bad things happen to the main character instead of things going their own way. From this conversation, the comedic Konosuba and the tragic Re:Zero were born.
Since they were very good friends, it was obvious Nagatsuki knew some of the secrets about Akatsuki. According to the tweet, Nagatsuki knew about the light novel “Combatants Will Be Dispatched”. He told Kadokawa Sneaker Bunko imprint that Akatsuki was hiding the manuscripts. So the credit for all the fame Akatsuki has got and we could enjoy “Sentouin, Hakkenshimasu” is because of his good friend.
Kadokawa published Akatsuki’s light novel in November 2017. The book currently has 6 volumes and is still ongoing. Media Factory’s Monthly Comic Alive is publishing the manga adaptation since March 2018. An anime television series adaptation by J.C.Staff premiered in April 2021.
As Wikipedia explains the plot as,
Having almost completed their conquest of Earth, the evil Kisaragi Corporation has decided to expand their operations to other Earth-like planets across the universe by sending Combat Agent 6 and newly developed combat droid Alice to a fantasy-like world via an untested teleporter. Shortly after arriving, 6 and Alice find themselves drafted into the Kingdom of Grace’s military. However, 6 has to collect enough “Evil Points” to help Kisaragi establish a foothold on this new planet. 6 and Alice must balance their work for Kisaragi with saving the Kingdom of Grace and its Princess from the encroaching demon army.
To show more about Nagatsuki and Akatsuki’s work-life friendship, Kadokawa also released the “Re: Zero Hajimeru KonoSuba Seikatsu” collaboration book in December 2016. It was a collaboration of the two high-ranking anime of that year. Furthermore, a Konosuba and Re:Zero Crossover short story exists. There, Tappei tells the story of Emilia in the setting of Konosuba, while Akatsuki writes the story where Rem is the one who goes on adventures.
Source: Anime Corner