"Men, prepare for new assignment!"
Field Commander is a unit that appears in the Star Wars: Empire at War and its expansion Forces of Corruption. It can be purchased by both sides at Tier 3 at either the Imperial Barracks or the Alliance Barracks (depending on which faction you're serving) for 550 credits.
The Field Commander unit is identical for all sides, with appearance being the only difference: Empire has 4 stormtroopers guarding an Imperial Officer, while the Rebellion has 4 of their soldiers and an Alliance Officer. The Commander and 4 bodyguards all function as one unit and cannot be split up. Their only active ability is to Take Cover and thus gain a bonus in defence at the expense of movement speed, functioning the same as the ability of Stormtroopers, Rebel Soldiers and Missile Plex Soldiers. However, the commander offers passive health and sight range bonuses to all allied units fighting with him. These bonuses are obviously lost when he dies. However, he is no different in regards to health and firepower to his bodyguards.
This unit is only somewhat more powerful than the regular soldier units, and is vulnerable to the same things. TIE Maulers, MTPL-2a and T4-B tanks will run it over, Rebel Infiltrators and the Anti-Infantry Turrets will shred it in about 10 seconds, and the artillery will wipe them all out in one volley. Tier 3 Rebels hardly even need him, as Obi-Wan is far better at the support role. The Empire would also be a lot better off investing into their vehicles or proper heroes. In short, he's little more then a waste of a unit slot.