In February, the Portuguese army besieged Ferdinand and his troops in Zamora. But it was a harsh winter and the inclement weather conditions affected more the Portuguese, who were outdoors, more than the Isabellinos who were sheltered in the city. In less than a month Alfonso V broke the ring and left to Toro.
Ferdinad's troops went after and caught up with them about a league from the city and forced them to engage in combat. After three or four hours of a confusing fight the Portuguese king retreated to Castronuño with a portion of his troops and John, Alfonso's son remained at the front of the forces, retreating into the city where they took refuge. Some people believe that from a military point of view the Battle of Toro was a tie, but the point is that most of the Portuguese troops went back to Portugal (so did Joanna), and Joanna's supporter in Castile was pretty much abandoned.
On September 1475 Alfonso V signed an alliance treaty with Louis XI of France. In 1476 French troops tried to force their way into a strategic border in Fuentebarría, albeit unsuccessfully. Ferdinand took the opportunity to secure his position in the Kingdom of Navarre and eventually the Aragonese king obtained some cities and the right to keep a garrison in Pamplona. This was a strategic decision so as to keep the French out of Navarre and thus protect Castile from that flank. In 1476 Alfonso V signed a truce with Ferdinand and Isabel, however he departed for France to try to convince Louis XI to get more involved. But France was immersed in a war with its deadly enemy: Charles the Bold, Duke of Burgundy and rejected his proposal.
There were several factors that tipped the scales in favour of Isabella's reign in Castile. The Battle of Toro was one of them, the Louis XI decision not to participate further in the war of Castilian succession and last but not least, the truce requested by Alfonso V. Juana's supporters had no choice but to accept and subject to their new monarchs. And that is the story of the unification of Spain.
If you would like to read what happened before, go to Part I