Overwatch, and the long argument about shooting on someone else's turn

If your side moves and then the other side moves, then for half the game you are watching. Worse, it makes a defensive position meaningless, because the enemy can walk across your line of fire in perfect safety as long as they stop before reaching you.

The fix is almost as old as the genre, and every version of it does the same thing: it converts a place your soldier is standing into a threat that exists when you are not looking.

X-COM: UFO Defense (Mythos Games and MicroProse, 1994) built it into the time unit economy rather than adding a button. Every action spends time units. If a soldier ends your turn with enough of them left, that soldier can fire during the alien turn, with the chance of it governed by their reactions stat.

This is the elegant version, and it is still the best one. There is no separate mechanic to learn. Spending everything you have is simply a decision with a known risk attached, which means the most interesting thing you can do with a turn is deliberately not use all of it.

Jagged Alliance 2 (Sir-Tech Canada, 1999) made the same idea active. If a mercenary has action points left and an enemy comes into view during the enemy's turn, play can interrupt, and you take control in the middle of their move.

The difference matters. X-COM rolls the dice on your behalf and tells you what happened. Jagged Alliance 2 hands you the moment and lets you spend it, which is worse for pacing and far better for the story you tell afterwards.

Fallout Tactics: Brotherhood of Steel (Micro Forte, 2001) had a different problem, because it could run in continuous time where nobody takes turns at all. Its answer was sentry mode: set a character to sentry and they open fire the moment an enemy appears, without being told.

That is the same mechanic promoted to a standing order, and it is what lets a squad in continuous time keep fighting while the player is busy with somebody else. It is a small feature that solves the real problem of commanding six people at once, which is that you can only look at one of them.

XCOM: Enemy Unknown (Firaxis Games, 2012) turned it into a declared action called Overwatch. Spend your turn watching instead of shooting, and the first enemy to move within your line of sight gets shot at. It is the clearest version ever shipped, and anybody can understand it in one go.

Then the arithmetic took over. If watching is a reliable way to shoot an enemy who moves, the strongest way to play is to not move either. Advance one tile, set everyone to overwatch, end turn, repeat. Players called it the overwatch crawl. It is slow, it is tedious, and it is correct, which is the worst combination a strategy can have.

XCOM 2 (Firaxis Games, 2016) answered with mission turn limits, and Firaxis said plainly that the timers existed to stop players inching across the map on overwatch. It worked and it remains the most argued-about decision in the series, because the fix for a boring optimum was to make carefulness itself expensive. Mods to extend or remove the timers appeared immediately.

Every version of this mechanic is trying to buy the same thing: a reason not to spend your whole turn. The genre's deepest tension is that spending everything is usually the efficient move, and a game where efficiency is also tedium has a design problem rather than a difficulty problem.

The lesson across thirty years is that reaction fire needs a cost on both sides. X-COM charges you the time units you held back. Jagged Alliance 2 charges you the action points and the gamble of being seen first. XCOM charges you a whole turn, which turned out to be too cheap, so XCOM 2 charged the campaign clock instead.

This is where a real-time game with a pause stands somewhere else entirely. Nobody has a turn, so nobody can act out of turn, and a soldier with a loaded weapon and a line of sight is shooting by default. Reaction fire stops being a mechanic and becomes the normal state of the world.

Which means the interesting question flips. In a turn-based game you ask when to hold something back. In real time you ask when to hold fire: when to walk past, when to stay quiet, when to let something go by because the shot is not worth what it starts. Commandos: Behind Enemy Lines (Pyro Studios, 1998) is built entirely on that question, and it never needed an overwatch button to ask it.

RAD Tactics is a squad tactics game for Windows, real time with pause, set after a collapse, with zombies and with factions fighting over what is left. It is in development, and we are not going to describe anything in it that is not finished.

What this history is useful for is the warning in it. A mechanic can be clear, popular and still quietly make the optimal way to play boring. That is worth checking for before anyone else finds it.