Not much is known is about the war but we know that the Autobots were outnumbered and outmatched by the Decepticons as seen in dark of the moon the Autobots launched ship called the ark carrying their leader sentinel prime and his crew. The ark was attacked by several orbital fighters and was hit by mini rockets causing it to go deepspace killing the crew and putting sentinel in status.
we also see in transformers the first movie of Megatron killing a straggling Autobot with an arrow going through the poor bot’s spark. In the last knight Optimus Prime said Megatron started the war, but was told by Quintessa during which she was brainwashing him that he did and he doomed Cybertron.
Many Autobots in the movies saw the war as lost, on earth they were able to win, but on Cybertron they were outmatched and had less numbers, Sentinel Prime even said “they were never going to win the war”, prompting a deal between him and Megatron. The Nemesis also crashed during the war where The Fallen soon arrived, it is believed that a battle took place on the ship causing it to crash.
Battle of Iacon and over the Allspark (Seen in dark of the moon and transformers one)
Space battle of the ark (seen in dark of the moon)
Battle of the Nemesis (possibly)
Autobots: Bumblebee voice box, Sentinel entire crew, Sentinel prime injured into Status, Unknown amount of death but believe to be higher than the Decepticons.
Decepticons: one orbital fighter carrying one pilot, Unknown amount believed to be lower than the Autobots