Three Knights Defense:

The Three Knights Defense, is a popular 'Open Game' opening played by white, which usually leads to tactical positions - giving plenty of options for White. The opening is fairly popular with beginners who strictly adhere to the opening principle: "Develop knights before bishops." It was one of the workhorses in the family of the Open Game, at even the highest levels, until World War I. Thereafter it fell by the wayside, along with a number of open games. This opening very quickly can transpose to the Four Knights Game and is very similar to the lines of that you may have seen in the Four Knights Game

     

Here is a list of the 4 most popular continuations in the Three Knights Defense:

a) Scotch Variation
b) Halloween Gambit
c) Winaver Defense
d) Steinitz Defense
 

 Scotch Variation

Exchange.jpg

Halloween Gambit

Berlin.jpg

Winaver Defense

Spanish.jpg

Steinitz Defense

Famous Games with the Three Knights Defense:

1) Scotch Variation - Srbis, J. vs Rambaldi, Francesco
2) Halloween Gambit - Klepaczka, T. vs Bulski, K. 
3) Winaver Defense - Bodek, Michael H vs Salimbagat, R. 
4) Steinitz Defense - Bereslavsky, M. vs Bunyatov, Rustam