Marshal Soult and the Siege of San Sebastian

After being defeated in the battles of the Pyrenees, Marshal Soult spent most of August re-building and re-organizing his army. By late August he was able to field a force of 45,000 men divided into nine infantry divisions. San Sebastian had still not fallen and militarily it made sense to leave it to its fate, however politically Napoleon would not be pleased if he did so. On 31 August he attacked with his army across the Bidassoa River in the vicinity of San Marcial and Vera. The attacks failed and San Sebastian eventually fell.

My questions is: what was the objectives of these attacks? Oman says in Volume 7 page 37, that Soult felt honor bound to relieve the garrison. But what does that mean? Pull the garrison out and abandon the city? Throw supplies into the city?

Thanks!

Bob