On Braavos, Wicket and her mother got word of the northern invasion. The loss of Portsmith was conveyed as well. They went to the Fleet's compound to ask for young captains to bolster the Brandon's Rest fleet. They found three young, brash captains willing to go to Brandon's Rest and take a ship. One was an offspring of Balerion Otherys, one Ternisio Otherys. One was an offspring of Tycho Nestoris named Ferrego Nesroris. And the last is a child of Ferrego Antaryon named Syrio Antaryon. Syrio demanded that they hire his entire crew, so three captains and thirty crew boarded the ship to the North. They unloaded on the east coast of the North and took horses to Winterfell. From there, they boarded the vehicle and were in Brandon's Rest in a few days. Welbi had paid them all for a year's service upfront.
The young Syrio was given command of the Portsmith because he already had a crew. The three captains were taught the use of wind power and instructed in the use of guns. They were agog at all the tech they had to learn in this strange, frozen town, but they were, and they got better. There was enough room at the shipbuilders' building, so they housed them there. Within a few weeks, they were carousing at the taverns and regaling the regulars with tales of Braavos.
The Zonian troops followed the trail left by the fleeing wildlings as it went unerring northeast and was joined by tracks from other villages as well. At last, they came within sight of the pass and saw wildling fighters defending the narrow cleft in the mountains. They set up their slings in the shelter of two small snow-covered hills and began their assault. The fighters in the pass retreated from the bombing, and archers moved forward to snipe at them.
That was when they discovered that the two small hills weren't really hills at all; they were snow-covered giants lying in wait. The giants shattered the slings and scattered the troops near them, and the wildings charged the archers. It was mayhem until a Zon general got them under control. One Zon soldier managed to get behind a giant and hamstring it; when it fell, it took out about 50 soldiers. The Zon archers were slaughtered, and the Zon general sounded retreat with about a thousand fewer soldiers under his command. Some 7,000 Zonian troops retreated to a defensible position a mile or so away. They checked the hills closely.
Tormund slapped the hamstrung giant in the shoulder and cheered his destruction of troops and machines. The giant sat up laughing, but the other giant said he needed to take his friend home to heal. The frost-fang leader gave them each a bag of gold coins and a large bag of meat, and the two giants made their way slowly north along the mountains. Tormund did not pursue the retreating Zon troops, but Nymeria and her pack did, picking off about 30 stragglers before they came back unharmed. Tormund ordered the men back into the pass to wait for the next assault. And the wildlings picked through the lost weapons and gear of the dead Zonian troops before returning to the pass. Many a cheer went up when magical swords and rings were found, and the general looting gave the wildlings great joy. They also found several wagons of food and sling ammunition. Tormund smiled at their victory, but he understood this was only the first assault and more were coming.
The Zonian general sent a few sleds' worth of men south to see if there was another way around these mountains. Those troops did make it around the southern edge of the mountains, discovering the wall. The troops on the wall made short work of them, and no word ever came back to the Zonian general.
In King's Landing, Bran was following the descriptions of these battles from the three-eyed raven and his men along the walls. It gave him happiness and somewhat tempered the loss of Portsmith, his personal friend. He understood there was more fighting to come and that an all-out war was still to come. There was no time to revel in these small victories, and yet they cheered him nonetheless.
The next few days felt like spring was in the air, even beyond the wall; melting was happening. But still the Zon came on, vowing to take the pass. The wildlings threw everything they had at them each time they rushed the gap, even using their sling ammunition by rolling it down the walls of the pass at them. Nearly 2000 wildlings died defending that pass, but they took 7000 Zon with them and a shocked Zon general. He didn't die, though they bundled him up with a few other survivors, and Tormund took them to Bran. The northern secret invasion was a huge failure, though no one in the far west ever heard what happened to it.