The war was a crucial period for the Tintin series. Indeed, during these dark years, Hergé made an extraordinary effort, both by continuing to invent and create new stories and, above all, by putting in place an ambitious programme to recast the existing stories, under continued pressure from his friend Charles Lesne, director at Casterman. Hergé had had him as a colleague when he worked on the newspaper Le XXème siècle. It was also thanks to him that the link was established with Editions Casterman for the revival of the Tintin albums based on Cigars of the Pharaoh.

Hergé told him about his method in a letter dated 29/3/42: "So, for all the stories between 'The Cigars' and the new one ['The Mysterious Star'] [...], I intend to cut and paste the original drawings...". Why L'Oreille cassée in the first place? Because it is the most densely-paginated of the "black and white" albums (132 pages), saving paper and making it possible to increase print runs.

Hergé began work on the album at the end of April 1942, with the aim of publishing it that year.

Hergé reassembled his plates, dropping a few squares that would be unpublished in the colour version of this album. Hergé will be giving these away to his friends and family in the same way as the covers of Le Petit XXème, as they will no longer be of any use to him!

On 22 December, Lesne stressed the need to speed up the current process: "Our ambition is to be ready with six or seven albums at least, by the end of the war, to launch ourselves into the conquest of foreign markets. [...] Whoever gets there first will have every chance of becoming 'king' of the market. [...] We are exceptionally lucky to have a 'golden' subject and hero for a prestigious launch, as soon as the post-war recovery begins". Hergé replied on the 26th, trying to be reassuring: he predicted that in the space of 27 months he would have completed 11 albums in colour, including three new ones! The rest of the story will show just how optimistic Hergé was!

It was not until 10 July 1943 that the albums finally went on sale in all bookshops at a price of 37.50 Belgian francs.

This is the original full-colour edition published in July 1943, known as the A20 (licence no. 1785-1786-1787) with a red pellior spine, of which "only" 15,500 copies were printed. That's almost half of the 30,000 copies of the Unicorn that followed.

The famous authorisation numbers were required by the German occupiers for all publications from 1943 onwards. They were to be found by all Belgian publishers, printed in very small print at the bottom of all books printed until September 1944!