His life spanned crucial battles and political turmoil as he fought to keep the Kingdom of Navarre independent alongside his brother Jaime Vélaz de Medrano y Echauz, mayor and alcaide of Amaiur-Maya, captain of the kings standing army, and royal guard of the monarchs of Navarre.

Juan Vélaz de Medrano's coat of arms was listed in the official archives of the Kingdom of Navarre.

Many principles are attributed to them by authors and historians:...for its antiquity, its splendor, for their military prowess and virtue and for every other value of chivalry that prospered with this family, in great numbers, magnificent and generous.

Around 1512, it was deemed a potential threat to Castilian control, leading to the appointment of a military commander, Colonel Villalba, as its governor.

Subsequently, in 1500, the Prince of Viana granted the royal castle and manor of Santacara to Juan Vélaz de Medrano due to his affiliation with the Beaumont family.

[1] The Prince of Viana then granted the Santacara estate and its royal castle to Don Juan Vélaz de Medrano y Echauz.

In October 1512, Juan Vélaz de Medrano y Echauz, Lord of Iguzquiza, went to war against the Castilian and Aragonese invaders led by Ferdinand II of Aragon.

[12] Juan Vélaz de Medrano y Echauz defended the royal castles of Del Castillo, Monjardin and Santacara.

After bravely fighting against the Castilian invasion, and following the conquest of Navarre by Ferdinand II of Aragon, Juan Vélaz de Medrano followed his legitimate king to France and participated in the unsuccessful attempt to restore the Navarrese Monarchy.

[1] In 1513 Don Juan Vélaz de Medrano was already listed among the quarter remitters of the merindad (administration and financial governance of the Estella region).

[13] After the regaining of Navarre's temporary independence, Juan's brother Jaime Vélaz de Medrano played a leading role in the defense of the legitimists as the alcaide of the royal fortress of Amaiur-Maya in 1522,[12] "having personified the Navarrese resistance to the Spanish conquest like no other.

"[14] In 1524, Charles V, Holy Roman Emperor, imposed travel restrictions on several notable figures, including Juan Vélaz de Medrano, lord of Igúzquiza.

[23] Juan's great-grandfather Juan Vélaz de Medrano was the fourth of the name, royal chamberlain of the Kings of Navarre and Aragon, lord of Iguzquiza, Arguiñano, Arzoz, Artazu, Zabal, Orendáin, the 1st lord of Learza, founder of the Vélaz de Medrano mayorazgo in 1437 (the oldest in Viana)[24] and the Royal Chamberlain of the Kings of Navarre.