Complex sentence: At a climactic moment, with the sun nearly set and thousands of warriors still between Arjuna and Jayadratha, Krishna realises that Arjuna was unable to reach Jayadratha before sunset.
Split into simpler sentences: At a climactic moment, the sun had nearly set and thousands of warriors were still between Arjuna and Jayadratha. Krishna soon realised that Arjuna was unable to reach Jayadratha before sunset.