Here's the scenario.
A group of 4 adventurers move into a room of 5 highly trained kobolds who employ group tactics. Their main strategy is shield walls with kobold-sized pikes. They try to form up but their initiative rolls are all over the place.
A shield wall works by everyone moving together, your shield protecting not only you but the soldier to either side of you and those behind you. If a soldier moves forward in front of the formation, not only are they exposed but there is a weak point in the formation that the enemy could exploit.
If the initiative is mixed up where 1 kobold takes a turn then 1 adventurer has a turn, then no matter what they do the shield wall will collapse as they won't be able to stay in formation.
How do I advance the shield wall without having gaps if the kobolds' turns are all mixed up?
Can I set movement as a reaction, so that when one moves, the rest follow? Can I have them skip a turn and so they all can move at the same initiative step?