Transformers: Scramble City
Japanese title: 戦え!超ロボット生命体トランスフォーマー スクランブルシティ発動編
Alternative titles: Transformers - Scramble City: Hatsudou-hen, Scramble City: Mobilization
Type: OVA
Source: Other
Episodes: 1
Status: Finished Airing
Aired: Apr 1986
Duration: 23 min
Rating: PG-13 - Teens 13 or older
Studios: Toei Animation
Producers: Takara
Genres: Action, Sci-Fi
Themes: Mecha

Beginning with a recap of the coming of the Transformers to Earth and the story of Devastator, the OVA then gets its original story underway, as the Autobots are shown to be in the midst of constructing the powerful "Scramble City," overseen by their newest arrival, Ultra Magnus. 

When the Decepticons learn of this, their combiner robots are deployed to attack, and a battle between them and their Autobot counterparts ensues. 

(Source: Wikipedia)