End of the Japanese Amphibious bonus is here....
At the risk of sounding uninformed, I can say that I'm not sure when the Japanese Amphibious bonus really ends. I thought it was 31 Mar 42. But in my current game, I performed a landing in early April 42 and did not incur the high disruption that I expected for being completely unprepped for the target. Unloading was very fast using merchant shipping. I changed my theory, and thought that maybe the bonus lasted until 7 Apr 42, as the manual says that it lasts "4 months". However, later in April, I did a divisional landing at Ambon with troops completely unprepped, and did not incur the drastic penalties expected. Now my theory is that it ends at 30 Apr 42. I haven't done a landing in early May yet to see the penalties.
I realize that I should know by now when it really ends. I thought I did. I'm judging my theory on my observations, which doesn't prove anything, but certainly changed my mind. My Ambon division should have been wrecked on landing, in my opinion, if the bonus had expired.
This is a long discussed topic, and one that I thought was settled, but it is not for me at the moment.
It might last until the 7th, never really checked that. But I have certainly felts its impact in supplies and especially motorized support unload rates....
You should be able to easily check this thru the unloading of supplies...a big difference between 250 and 1200. I will drop a message to NJP and get him to unload some supply somewhere and measure the unload rate before the 7th.
Depending upon your units experience, forts and terrain, the supply, disruption level and composition of the defenders, invasions with very little to 0 prep can be done with few adverse effects.
Although I don't think it mentions it in the rulebook, naval support in the hex being amphibously unloaded to is horrendously strong. Most people only see this when trying to unload large caliber guns at level 1 ports. In addition the dedicated amphib ships once empty help unload too.
Japanese units are generally really well suited to amphibious operations.