Sabotage at Hampton Roads was the final blow that broke GDI resistance in the area and allowed Nod to launch a full scale invasion of the Northeastern Seaboard Blue Zone in Command & Conquer 3: Tiberium Wars.
A war needs supply lines and supply lines need transport. Nod's offensive in BZ-2 was limited by the lack of a gateway to bring in large amounts of resources and equipment. To rectify that situation a cunning plan was created, to both cripple GDI logistics by depriving them of the largest naval base in North America and gain a crucial offload point for Nod supplies. Furthermore, GDI's aircraft carrier GDS Pathe was anchored in the port. An attack on the Langley AFB would take place at the same time the Hampton Roads would be attacked, leaving the carrier the sole provider of air support on the eastern seaboard. If all went according to plan, the skies would be clear for Nod within hours.
The plan itself was a masterstroke - a single Commando would be smuggled in via a container and take out the GDS Pathe, creating an opening for a small force to be dropped into the port. Then, this small force would destroy the port authority building, scrambling GDI communications and allowing Nod to land amphibious assaults along the coastline, securing the port.
You begin with a single Commando. Make your way to the Pathe and kill the infantry along the way (garrison the commando to minimize exposure to enemy gunfire, it's unhealthy). There are supply crates scattered around, collecting them is a good idea, as two at the beginning contain veterancy upgrades, which will bring the commando to elite level instantly. At the Pathe a Predator and an APC are stationed - blow up the barrels to take them out. A GDI commando will harrass the lady at the carrier - show him you do not treat women like that.
After the Pathe is sunk, Venoms and fanatics will arrive. Use the Venoms to scout the city and flush out the snipers. Once the road is clear, bring in the Commando and search the container storage for the lost saboteur. It is important to use the Venoms as much as possible and get them to Elite level - this will make the rest of the mission significantly easier, not to mention weathering the masses of infantry sent against your forces.
Using the Venoms as advance scouts, destroy the small outpost and slowly work your way towards the port authority building. Elite Venoms are very adept at taking out Pitbulls and other lightly armoured vehicles - make use of that. The small base should pose no problem if all four Venoms are elites. If you wish use the saboteur to capture a GDI command post which allows you to conduct air strikes against the defending enemy. Take out the power plants to disable the enemy defenses, then just mop up any stragglers with your patrol craft and blow up your target.