Episode 461

"The Beginning of the War! Ace and Whitebeard's Past!" is the 461 episode of One piece.

Summary
Three other ships, along with the Moby Dick, infiltrated the bay. Whitebeard himself from the deck of the Mody Dick, commenting that it would be better if his son, Fire Fist Ace, is alright.

Ivankov asks Luffy if Monkey D. Dragon will come and save Ace, as he would never let his son get killed. Luffy replies that although his father is Dragon, Ace's father is in fact Gol D. Roger.

Ace then remembers all the events that led him to being the Whitebeard pirates Second Division commander. (Parting with Luffy, his days of him as the captain of the Spade pirates, a meeting he had with Shanks in a winter island, etc.)

It also shows about his battles with Jimbei and Whitebeard, and later on his friendship the the rest of the Whitebeard pirates.

Trivia

 * When Ace meets Shanks, it can be seen that Shanks still has his two arms.