Shōnen Gahōsha launched its first manga magazine in 1948, being one of the early publishers to start up after the end of World War II. By 1950, it had rebranded this first magazine into Shōnen Gahō, this was another early example of the modern shonen manga and it was competitive with similar magazines from other publishers in this period. Shōnen Gahōsha remained competitive with the shonen manga demographic after the first two weekly shonen magazines (Magazine and Sunday) both launched in 1959, with Gahōsha launching Weekly Shonen King in 1963 (years before Jump and Champion).
This magazine lasted for decades and while it was competitive with the other four magazines, it didn't have many of the serializations that were widely embraced on the same level and in 1982 it slowed down to releasing twice a month before ultimately ending in 1988.
Though the published had already been a part of the early seinen manga market with Young Comic beginning in 1967 and running for several decades, when Weekly Shonen King ended, Young King took over as the premiere manga magazine for the publisher and seinen manga became the major focus. Young King has gone to to have various concurrent spin-off magazines like Young King OURs (where Hellsing was serialized), Monthly Young King/Young King OURs GH and a relaunched Young Comic.