VaultingFrog:

I veiw it as more of a symbol. If the Human race can set the tempo for a war/conflict they have that much more of a chance of winning that said war or conflict.

Retaking Harvest not only can give them a huge moral boost but it will show the enemy that the human race wont go quietly into the night. That they will fight for what is theirs and they will do everything in their power to win.

I personally think that Halo had some major insperation from the Babylon 5 series from the Sci-Fi channel. In particular their prequel movie, In the Begining where the human race was almost wiped out during a war with another race. They struggled on for 2 years, actually ramming their ships into the enemy in an attempt to make them pay with blood for every planet they took. They were out numberd, and were severly out tech'ed by this race and yet they held them off for 2 years of bloody struggle. That is power to me.

And again you all have pointed out how strategic this action was so I wont bother posting on that part of the subject.

 

The ONLY person in here with the correct answer.

 
The retaking of Harvest was a symbolic move by the UNSC, to boost moral, and to keep the hopes up for the home front.  Remember, there are always two fronts in every war, the guys you fight, and the people back home.  If the government doesn't have the moral support of its people, then absolutely no war can be fought.  Which is also the reason why the Spartan program went public, as well as the media getting edited news about the war.