This is prompted by a lively exchange on the 15mm SF page on facebook.
Later Ganesha rules now have the principle of using reactions but older titles can be "upgraded" quite easily.
Way, way back when we was doing LARP pirates I looked around for a set of rules that could do small unit actions. By chance there was the new Flashing steel. The results we got were so similar to real combat that we were 'ooked. Now there's an add-on that really reproduces the rolling chaos that is combat.
If your rules still use yougo-Igo, welcome to the real world-. Reactions speed up games and can be confusing as who's turn can become lost-. Try using different colour dice for reactions, it helps.
You have to appreciate the genius of the simplicity of this method. Most rules don't try. At least one does so clumsily that many players (in my experience) won't play. Simply, the lower Q opponent is more likely to fail and the higher better able to seize the day. He who dares wins.
To recap, when you roll for actions you often fail 1-2 dice rolls. As a reaction, your opponent can "seize this advantage", rerolling your fails and taking effective action.
This can be very effective so you can reduce the impact, here's some suggestions based on other rules:
you can only have one reaction attempt per unit
choice of unit is by similar rank, quality i.e. a CO can benefit from a CO but not a rank n file
only one reaction can be used - 2 fails just gives you 2 choices
not a combat action, but you can shoot and/or move into contact
reactions go first or simultaneously
Warning, this makes modern move, shoot & spray weapons very, very nasty. We used it here in game 3 and I got cheesed-.
You can also use reactions of both sides to govern the erratic movement of an "NPC" force such as fleeing scientists, refugees or herds.
Here's an example from our early test of Song of Spear and shield. Achilles had been coming on strong, an armoured hero armed with javelins every move forward got a free shot and he couldn't miss. Tony used the rally back option to withdraw and reform. My activation, 2 fails (being a hero, he gets one!) In Tony's front rank there was a better quality archer who took the 2 fails- success. With 2 he does an aimed shot and rolls a 6. Achilles rolls a 1. He's not only dead, that's a Harold, gruesome death. Of a CO. Most of mine rout on the spot-. A simple rule, units having 2 simple stats, not 5-6 or more. A few add-ons. This is quality.
You may remember that Achilles was badly wounded by an opportunistic arrow shot. You can take the fail as a trip or a distraction. If you've ever been there-.