At the outset of 54 BC, two things certainly troubled Caesar. Lucius Domitius Ahenobarbus, a definite political opponent in the camp of the optimates, had been elected Consul, and trouble was brewing in his province of Illyricum. The Pirustae tribe, near modern Albania, was causing trouble forcing Caesar to focus some attention on his neglected province. With the presence of the now awe-inspiring Caesar, the situation was handled quickly by raising an adequate force. The Pirustae provided hostages and settled into peaceful affairs, allowing Caesar to return to Gaul.
While away, he ordered a massive fleet to be built for a larger second crossing to Britain. This time though, Caesar made modifications to the ships, having them built without the deep keels of standard Roman galleys. This would allow a more effective landing for his legions and cavalry. By July of 54 BC, after a short delay caused by the Treviri tribe, Caesar was finally ready to go. With 800 ships, 5 legions and 2,000 cavalry, leaving 3 legions and 2,000 cavalry in Gaul under Labienus, the Roman fleet was the largest naval landing operation in the history of world, and remaining so until the D-Day invasion of Normandy in 1944.
Landing the following morning, the sheer size of the Roman force surely intimidated the Britons. The Romans were allowed to land and make camp freely without opposition, subduing several local tribes in the process. The main British forces retreated inland to avoid Caesar, but he definitely pursued. One legion and 300 cavalry were left at the beach camp, while the bulk of the force marched towards the Britons. Small scale fighting couldn't stop the Roman advance and Caesar captured one hold out near modern Canterbury on the Stour river. Just as Caesar was about to press the issue, however, news arrived of another coastal storm that wrecked the bulk of his anchored fleet. Hurrying back to the camp, he ordered Labienus to build as many ships as he could in Gaul, and ordered his own men to repair the damage.
Successfully salvaging his fleet, Caesar returned to the Stour to find that the Britons had begun to unite under a Cassivellaunus. While marching, the Romans were ambushed but repelled the attack after some serious casualties and a hard fight. Next, the Romans moved to the Thames and were engaged in the largest battle of this expedition. Winning a decisive victory, the resistance of the local tribes in any significant numbers came to an abrupt end. Caesar invested the fortified hold out of Cassivellaunus while his single legion back at the beach camp fended off a joint attack of various tribes. Winning both engagements, the opposition of the local tribes came to an end, and Caesar was able to claim victory.
By September, arrangements for peaceful relations had been made, and the Romans returned to Gaul. Though this second invasion of Britain did little more than secure some hostages, tribute and Roman awareness on Britain, it had the significance of being a dignity saving campaign for Caesar. After virtually retreating from the first expedition a year earlier, this time he left only after securing his dominance. Though that dominance wouldn't last without a Roman presence, Caesar was able to claim victory in a land that some probably didn't' even think existed.