Imagine a round 3 situation:
Italy has its fleet in SZ 15, they maybe attacked Transjordan in round 2.
a clever move would be as UK - move your complete fleet to SZ 13, this fleet should be AC + 2 ftgrs, 2 Cruisers, 2 DDs and 1-2 subs. Yes, buy subs as UK if you want to kill that Italian fleet.
So that Italien fleet is trapped!
If they control Egypt and Trans Jordan, use your Inf from Persia and a Bomber to capture Transjordan, so the Italian fleet can't escape via Suez canal.
So what can Italy do ?
1) Attack - that's suicidal, especially with 2 UK subs and that Russian sub in SZ 13 (russian sub moved to SZ 13 first, UK followed)
2) leave - unfortunately they can't ; SZ 16 is also 2 spaces away from SZ 13
3) block - the best option.
This is a 2 step move:
First take ground units from Italy and recapture Transjordan
Build a DD in SZ 14 hoping to block UK fleet and use Suez canal next round.
Now the Russian sub will have a use.
Attack that newly build Italian DD with your sub and 1-2 fighters from Caucasus (you have to land all your Russian aircraft in Stalingrad or build new one there !!). SZ 14 is 2 spaces away from Caucasus, so that fighters can fly back in NCM safely.
It doesn't matter if that sub survives, what matters is to destroy that DD - UK will move before Italy and will destroy that fleet easily ! (use 2 subs and 1 DD plus aircraft, you will win with overwhelming odds - do not use your cruisers if not necessary, better attack France if possible but beware of German aircraft)