For those that are interested and curious, the Japanese title of 1026 is 天王山.
天王山 was translated by leaker as the "the decisive battle", but there is also another reference that is widely used.
天王山 usually refers to the battle that turns the tide of an evenly fought war.
An example of a battle of 天王山 would be the game 5 of a NBA finals when two teams are tied at 2:2.
Game 5's win would give a huge momentum to the winning team.
In the case of 天王山 of chapter 1026, the alliance has seemingly won the decisive battle by having luffy sky-split with kaido and beating jack + candy man.
This is basically Oda's round-about way of saying the sky-splitting moment is basically the turning point of the war.