However, fundamental differences seem to have started to develop since the mid-1970s. Following the discovery of intelligent life on Minerva, both superpowers engaged energetically on efforts to launch a manned spacecraft there. This evidently had an effect of exacerbating tensions on Earth, with American and Soviet planes engaging three times in direct aerial combat over Beirut – presumably drawn, after the Israeli Invasion of Lebanon in 1982, into a far deeper involvement than in our history.