Complex sentence: It was understood that Hideyoshi was at least 4 days march away however as soon as Hideyoshi learned of Sakuma's actions he led his men on a forced march through the night and reached shizugatake within a day and a half.
Split into simpler sentences: It was understood that Hideyoshi was at least 4 days'march away during Sakuma's attack. However, as soon as Hideyoshi learned of Sakuma's actions he led his men on a forced march through the night and reached Shizugatake within a day and a half.