Note 1: UK can bring 2 TRN not 1 to the fight on UK1 (the WCan TRN can reach SZ7 also)
On with the analysis…
So the initial fight is:
UK: 2 TRN (fodder), 1 BB, 2 FIG, 1 BOM
Germany: 1 TRN, 3 SUB, 1 DST
The odds on that fight are 97.5% for a UK win
Even with “Chicken Subs”, the odds are less than 1 in 10 that any German SUBs survive.
But let’s say that a couple of them do…
USA strafes them with their BOM on USA1, probably sinking another one (now you are down to something like 1% chance of 1 German SUB alive)
And the Russian SUB comes in for a swipe on R2, or just joins the party…
Add in a UK build of an AC and DST…
G2 Battle in SZ7 looks something like this…
1 SUB (AT MOST, but probably none)
5 FIGs (assume 1 FIG dead in Ukraine)
1 BOM
(I am blocking the SZ13 BB and TRN with 1 USA TRN that landed 2 units in Algeria)
Allied Forces:
1 BB, 1 AC, 2 FIG, 1 DST, 1 SUB
Axis wins only 28.1% of the time; with the odds being that UK retains their capital ships, and Germany is missing most of their navy and their entire air force.
Meanwhile, Russia moves into Balkans, Belo, Ukriane and liberates Karelia…
After the SZ7 route of Germany, the US sails to SZ12 with multiple DSTs, an AC, TRNs, and FIGs, blocking the remnants of the Geran Navy from getting out of the Med, and setting up a solid shuck into North Africa.
Net Result:
UK is slowed by 2 turns landing units in Europe or Africa.
Germany is out an Air Force for the entire game.
I call that a pretty BAD move for the Axis.
In fact, barring horrid Allied play, I have yet to see a Channel Dash/Fleet Unification strat that was worth the cost to Germany.