personally i use them for pawn breaks and defense, but im not too sure on how to properly use them
How do I use the alfils in chaturanga

I started playing shatranj a few days ago, but haven't really found comprehensive literature on the alfils. Should I use them for pawn breaks? Save them for the late game? Defend key squares? It seems like any tactic is quite easily refuted due to the limited mobility.
One al fil ( Persian piece ) can moce only in 8 squares in board. It is more for other pieces like as the name of the game 'catur ańga' that suggest strategy. It is oftem to sacrifice but in this gamę you should think about all , not about one piece.
Squares d7, e7 are useful squares for the knights if the c, f pawns already occupy c6 or f6, so in this case restricting mobility is useful (same for white mirror).
Sacrificing is also a common motif, if opponent captures an alfil that is restricting mobility, can recapture with a pawn and still restrict mobility.

I started playing shatranj a few days ago, but haven't really found comprehensive literature on the alfils. Should I use them for pawn breaks? Save them for the late game? Defend key squares? It seems like any tactic is quite easily refuted due to the limited mobility.
Well, nice question... This is the question of all Shatranj questions! I can't answer in short because there are too many things to say. I think you can recognise an expert player from a beginner through the way they make use of their Alfils. Our best player @coolthing even invented an opening system (tabiya) with early activation of both Alfils. However in another known opening the Alfils don't move at all, they just sit there where they are! There are several ways... Personally I consider the Alfils as 'flying pawns', and this implies they are generally better than a normal pawn, but not much better. So I'm not happy to exchange my Alfil for one pawn (unless it is a central pawn which is almost equal), but I'm fully happy to exchange it for two enemy pawns! (especially two adjacent ones, because this would make a big hole in the opponent's defense). In fact "an Alfil for two pawns" is a basic tactic, which often beginners fail to see. This is a good starting point I think.

Alfils are one of the lowest-value pieces. I value them at 1.5 pawns (but I imagine engines may be different). Since the four alfils on the board cannot interact, it is rather difficult to "trade" them, so there are a few things that can be done:
- Capture any piece (Ferz, Knight, Rook) - all of these pieces are more valuable, so if you can trade your alfil for one, it's usually a good trade. As mentioned by @samuelebeckis, an alfil for 2 pawns is also an advantageous trade.
- Sacrifice it for a pawn and positional advantages - could be extra space, open files, better control of certain squares, or preparation for a pawn storm; you don't need a lot of compensation for this trade to be worth taking.
- Control key squares - by which I mean secure the alfil on c5/f5 to control e7/d7, which are common developing squares for knights and the ferz.
Here's a game involving a double alfil sacrifice to create a pawn storm: https://www.chess.com/variants/chaturanga/game/38459547/0/3
I started playing shatranj a few days ago, but haven't really found comprehensive literature on the alfils. Should I use them for pawn breaks? Save them for the late game? Defend key squares? It seems like any tactic is quite easily refuted due to the limited mobility.