ORIGINAL: Lowpe
... My biggest worry is figuring out how to counter SigInt that Allies get. Both on ship destinations, and infantry prep for the landing sites...
1. You can use waypoints to disguise your task force destinations.
For example a task force could start from Pearl Harbor with destination of Pago Pago but waypoint #1 is set to be a few hexes short of the actual landing site on the West Coast. To avoid the TF resuming it's course towards Pago after reaching the waypoint, set a loitering delay for waypoint #1. Also take into account the range and location of Allied air search assets as it would be rather inconvenient for the TF to be discovered en route to it's waypoint. Notwithstanding the increased risk, travelling silent ie no active search planes or defensive CAP from the accompanying CVs and BBs/cruisers would also have to be employed.
2. You should also employ decoy invasion TFs.
The destination of the decoys should be well away from the real landing site. Include some heavy LCUs with the decoy destination as their objective even though they are intended to be second wave follow up forces for the real invasion. You can subsequently reset their objective whilst at sea. Make certain the decoys are spotted. Ideally the enemy takes the bait and moves reserves to cover a landing in Canada/Oregon which will give you a few days breathing space at the real landing site in California. You can race the decoys to the real landing site probably quicker than the enemy can recall the troops sent up north.
3. As part of the invasion maskirovka for a few days before "landing", switch your aircraft to port attack missions to hit coastal guns first and defending LCUs second at the decoy invasion site. Surrounding airfields would be targeted with airfield attack.
4. There is nothing you can do about hiding the LCU objective except for one very dangerous gamble. Very highly experienced LCUs can now retain a part of their previous objective level when switched to a new objective. Not recommended as far too risky for the sort of operation you have in mind but an option. Obviously best employed with any decoy LCUs.
5. In deciding what will be the decoy invasion site, pay close attention to the transportation network.
Remember USMC and USN LCUs cannot employ strategic road movement but can employ strategic railway movement. Also take into account the static coastal gun locations. Choosing a poorly defended static coastal gun position for the decoy site lends greater credibility to the maskirovka. Especially if some LCUs have an adjacent non base hex as their objective; the "intention" being to cut off enemy reinforcing LCUs from employing strategic movement into the decoy site.
Alfred