I’m not sure about the sword and shield stuff. The rule book makes no mention of those items.

Regarding the subject of tacking in front of a starboard tack boat the rule is not that complicated. (Getting the facts nailed down off the water does tend to be complicated.)

Consider a port and starboard tack boat (Rule 10 we understand) Port must keep clear of starboard.

Then what if the port tack boat begins a tack?

The boat is still on port tack until she is head to wind (still Rule 10). When she reaches head to wind she is tacking (Rule 13) until she is on a close-hauled course (defined by the direction the boat is pointing). During this time the tacking boat must keep clear.

When the tacking boat reached a close-hauled course Rule 13 stitches off and Rule 12 goes into effect. That is provided the starboard tack boat is still clear astern of the boat that just tacked.

At this point the boat clear ahead (the one that just tacked) has the right of way. But because she gained the right of way by her own actions she must make sure the boat behind has room to keep clear (Rule 15).

What this means is that once the tacking boat is on a close-hauled course on starboard the boat approaching from behind must maneuver promptly in a seamanlike way to avoid the boat that tacked.

Now if the boat behind had to start avoiding before the tacking boat was at close hauled then the tacking boat fouled. Also if the boat from behind didn’t start to avoid until after the tacking boat was on close hauled but had to do so in an un-seamanlike way to avoid collision then the boat that tacked also fouled.

But if the boat from behind begins to avoid when the tacking boat is on close-hauled and is able to avoid her by maneuvering promptly but in a seaman like way then there is no foul.