The Vale

299 AC

 * When conflict first breaks out between Houses Stark and Lannister, the Vale initially stays neutral, despite Lady Catelyn Stark’s pleading to her sister Lysa Arryn. However, when Edric I Baratheon asserted his position on the Iron Throne, the Vale pledged allegiance to the new King, especially after the deceased Lord Jon Arryn had cooperated with Stannis Baratheon to lay the ground for declaring Joffrey Waters and his siblings bastards born of incest.
 * After Lord Petyr Baelish, a minor Valeman Lord and Master of Coin, conspired with Lord Paramount Renly Baratheon to place King Edric on the Throne, he is named as one of the Seven Regents for the Boy King and serves until Edric I reaches majority in 303 AC.

353AC- Targaryen Invasion

 * House Arryn sent Knights from the Vale to aid in the war against the Targaryen invasion. House Arryn remained loyal along with a majority of the Vale Houses.
 * The few houses that refused to aid in the invasion of the vale sent wards to the Eyrie to make amends.

Second Coming of the Andals
Andals living North of Pentos are pushed out by powerful Pentoshi looking to aggressively expand. The refugees form an invasion force and sail to Westeros. Like their ancient predecessors they too land in the Vale. Splintered by storms, two groups land scattered. One near Gulltown and the other nearer Coldwater. Lord Osric Arryn and his brother Lucas dispatch Knights to put down these Second Coming Andal invaders. Having supplanted the First Men, the Valemen would not have their lands taken from them by these pseudo Andals from Andalos. Primitive relics of the Faith of the Seven are acquired and brought back to the Eyrie for safekeeping. Among the relics are ancient and delicate scrolls of long since forgotten Septons.