There are multiple victory conditions in Advance Wars By Web, not all of which are possible every game.
When a player loses or deletes their last unit on the map, they are eliminated from the game. If the game has 2 or more players still on the map, the defeated player's properties will turn neutral, with their HQ turning into a neutral city. The last player (or team) standing on the map is declared the winner.
Capturing a player's HQ will immidiatly remove them from the game, regardless of their unit status. If the game has 2 or more players still on the map, the defeated player's units will be deleted, and all of their properties will be given to the player who captured the HQ, the HQ itself turning into a city. Note that if an army has multiple HQs on the map, having any one of them be captured will remove them from the game.
If a map has no HQs placed on it, any Labs pre-owned by an army on the map will function as HQs for the game. If a player loses control of all labs on the map, they will be removed from the game as if they were routed. If an army has more than one pre-owned lab on the map, they must lose control of all of them in order to be eliminated from the game.
If the game's "Capture" option is set to a number, the first player to hold the amount of properties set in the option will be declared the winner instantly upon the limit being reached. HQs, Bases, Ports, Airports, and Cities count as properties for the sake of this condition, while Comm Towers and Labs do not.
If the "Days" option is set to a number, the game will play as normal, until the set day has been reached. If there is no winner by the time the day limit has been reached, the player with the most properties (following the above rules of property count) will be declared the winner. If there is a tie among the players with the most amount of properties on the map, the game will be considered a Draw.
If a player wishes to surrender in the game, they can click the [Resign] button whenever it is their turn. The game will confirm whether or not they do wish to resign, and if they do, they will be eliminated from the game as if they were routed.
Similarly, if a player fails to take their turn within the alotted Boot Interval, the player will be ejected from the game, functioning exactly as if they had resigned. If a player has their turn ended by the Automatic End Turn (AET) Interval twice in a row, they will be booted from the game as well.
If a player would like to offer the game as a Draw to their opponent(s), they may click the [Set Draw] button at any time, even if it is not their turn. This will notify all players in the game that at least one player has offered a Draw, but not which or how many players have actually offered the draw. If all remaining players in the game have [Set Draw] on, the game will immediately end, declaring it a Tie between all remaining players.