If the Jews will walk in G-d's ways, they will leave peacefully in the Land.
"The Word of G-d will thus be for them instruction by instruction, instruction by instruction, measure by measure, measure by measure, a bit here, a bit there, so that they go and fall backwards and become broken, ensnared and trapped." - Isaiah 28:13
Because the people of Yehudah could not bear to learn the Word of G-d - even one instruction and one measure at a time - therefore G-d will "instruct" the gentiles to mete upon them a "measure" of retribution for every measure of Yehudah's sins and to exile them among the nations, spreading them "a few here and a few there." Let them fall into national decline and be trapped amidst mighty nations.
"So listen now to the Word of G-d, you scoffers, leaders of this people in Jerusalem." - Isaiah 28:14
But not only did the people disregard the Word of G-d, unwilling to learn even a bit at a time, they provocatively scoffed at the words of the prophets who spoke the Word of G-d. And the people's leaders who should have known better and were supposed to be their spiritual guides, were instead the leaders in scoffing at G-d's Word.
"And now, do not scoff, lest your chastising become more severe. For I have heard from G-d, the Lord of Hosts, of complete destruction upon all the Land." - Isaiah 28:22
Once again warning against scoffing at his words, Isaiah adds that doing so would worsen their lot - exile will be transmitted to complete destruction.
Isaiah now offers a parable for the change from Yehudah's success to their subsequent downfall (Cf Isaiah 28:23-28): A farmer does not work randomly - everything he does has a plan and an order. He first must plow the field and level its surface before it is ready for planting. And when he plants, he does so in a specific order, also planting each seed in a different way. When the seeds grow and are ready for threshing, each one is threshed in a different way. Who teaches him this, who instructs him in action? it is G-d Who guides his way.
"This, too, comes from the Lord of Hosts, Whose counsel is wonderous and Whose wisdom is great." - Isaiah 28:29
And the parable is that G-d's Will has not changed, rather it is all dependent on us. Just as the farmer does different things that all serve to achieve the same goal, similarly G-d grants success or downfall depending on what we deserve. Yehudah's destruction was like the threshing of bread grains which must be thresed with a heavy wheel. But essentially the exile is just the "planting phase" to disperse them to where they would grow. Being in exile would "teach and instruct" and eventually, G-d will reap them - He will not thresh them forever.