I've read this article published on blogs.magicjudges.org explaining the combat shortcut which is about (contrary to the normal proceeding) the Not Active Player (NAP) receiving priority prior to the Active Player (AP) in the Beginning of Combat step (BoC).
This is also stated in the Magic Tournament Rules:
If the active player passes priority with an empty stack during their first main phase, the non-activeplayer is assumed to be acting in beginning of combat unless they are affecting whether a beginning of combat ability triggers.Then, after those actions resolve or no actions took place, the active player receives priority at the beginning of combat. Beginning of combat triggered abilities (even ones that target) may be announced at this time.
At the end of the article the author mentions that normally this is not a problem since most of the time the AP does not want to act first anyway. However, one scenario in which the AP wants to be the first one to receive priorioty in the BoC step is mentioned:
AP Acting First in Combat
The new structure makes it look like the active player can’t be the first person to act in the beginning of combat step. That’s not true, but it does reflect the fact that the active player needing to act first is unlikely. The only scenario I’m aware of is holding a split second spell while your opponent is floating mana, which is not something that’s going to come up every day! In that situation, the protocol is the same as ever – you ask your opponent if they want to do something with that mana in the main phase. If they do, you’re still in main phase, since they used mana they couldn’t use in beginning of combat, nullifying the default.
Otherwise, there is a way to do it, but it does give the opponent some information. While in your main phase, simply say “I do this thing in Beginning of Combat”. Done! Of course, the non-active player has the ability to interrupt and do something in your main phase. That’s not really any different than it was under the previous shortcut.
However, I can't reconstruct an example for such a scenario from the information given in these two paragraphs. The following information is given as stated in the paragraphs:
- NAP has mana floating in the first main phase
- AP has a split second spell
Question: Can you give an example for this scenario in which in order to reach his or hear goal, AP needs to be the first one to to receive priority in BoC to then cast the split second spell?
To illustrate the difficulties I have with this, here is an example which doesn't work:
- AP is in his main phase, controls a Grizzly Bears enchanted with a Rancor. He has a Sudden Spoiling in his hand and enough mana to cast it.
- NAP has 2 life, controls an Endbringer and has one mana floating.
- AP wants to have priority in BoC to then cast Sudden Spoiling. He does not want to cast Sudden Spoiling in the main phase because NAP has floating mana he or she can use to respond. If everything goes well, AP then can attack with his bear (4/2, trample) and win the game (NAP now has a 0/2 creature).
This example doesn't work because of several aspects:
- Why does AP need to have priority in BoC to cast Sudden Spoiling before NAP receives priority? Why does AP not let NAP have priority first in BoC, NAP then passes priority, then AP uses his priority to cast Sudden Spoiling?
- Why doesn't AP cast Sudden Spoiling in his main phase? Sure, NAP has mana floating, but he can't use it to activate Endbringer's cant-attack-ability in response anyway because Sudden Spoiling has split second.