Originally Posted by
Helden
The Blackfish himself states that he doesn't have a lot of men when talking to Brienne, now ofcourse a few men can hold a well situated castle for a long time, and Riverrun is very well situated. But in the end, everyone in Riverrun would die. Honour matters nothing to the dead.
Now, lets look at the Tully words, Family, Duty, Honour.
Family - Edmure saved his family, he saved his son, his son who other than himself, is the last Tully left alive. Except for the Blackfish ofcourse. Who had already stated that he wanted to go down fighting. Its not really a difficult choice, let an old man live for a few years more, and then eventually die, or save a young child.
Duty - Edmures duty is to his people. He saved his people, he saved his castle. Once again, its an easy choice, let the siege continue, watch Riverrun be destroyed and what its people either be slaughtered when the castle is taken by force, or starve to death a couple of years down the line.
Honour - Honour doesn't matter to the dead, i'm a firm believer in the quote from Mass Effect "Stand in the ashes of a trillion dead souls, and ask the ghosts if honour matters. The silence is your answer".
Now as to the "2 years of provisions", and maybe holding out long enough for the North to come down and save them? Where is this army going to come from? The 2 biggest armies in the North, that being the army of the Boltons and all there Bannermen, and the Wildlings/Houses that have joined up with Jon and Sansa are about to batter themselves bloody at Winterfell, so neither army will be in any state to then march south and fight there way past the Twins (as has been previously stated, the only way to get an army from one side of the Trident to another, that being the reason that the Freys even have power). So that leaves the Knights of the Vale, who maybe under the command of Lysa Arryn, might have come to help them, but they aren't anymore, they are under the command of Littlefinger, what does Littlefinger have to gain by going up against the Freys, who being Lords of the Riverlands now, would also call there banners and by extension the Lannisters and the Crown? Nothing at all, so it wouldn't happen.