The Second Cylon War began with a massive surprise strike against the Colonies by the Cylons. Nearly all Colonies were attacked at the same time, a quarter of the fleet was destroyed in the early hours and civilian losses ran into the tens of millions.
Many Battlestars found their systems disabled during the fighting, seemingly remotely switched off by the Cylons using a backdoor in the Command Navigation Program. This vulnerability meant the loss of hundreds of ships in the initial engagement. Only a handful of Colonial ships had not been upgraded with the CNP, while others were saved by a faulty update, which by sheer coincidence prevented the Cylons from accessing the targeted ships, though many were lost to sleeper viruses and logic bombs later on.
For three days the Colonial fleet fought for the survival of Humanity. By which time nearly half the Fleet was lost, but the Cylons withdrew with substantial losses and the Colonies struggled to regroup.
One of the first casualties of the war was President Adar. Many other cabinet members were killed or severely injured, leaving the secretary of the Treasury as the new President.
Within days reserves were called up and tens of thousands of volunteers joined up with the Fleet, reserve ships were hastily rearmed and refurbished and long range patrols were sent deep into Cylon space.
The fact that the Cylons had been able to attack all Colonies simultaneously, meant that they had an increased jump range and that no system was safe from attack. Extending the safe zone would be the primary concern for the Fleet in order to buy the extra vital minutes to prepare defences in case of another attack.
Meanwhile the Fleet prepared a strike force that would look for the Cylon homeworld and annihilate the Cylon presence once and for all.