When it is your turn, WL will try to execute your next order. However, if the next order cannot be executed for whatever reason (most commonly because you've already lost the territory where you tried to attack from), WL skips that order and goes on to the next, until it finds an order which can be executed.


An important detail is that orders which, for whatever reason, work out to having zero armies actually do something count as "not executable" in this sense (a common case: attacking from a territory with exactly one army on it). Note this is not the same as affecting zero armies. A great example is indeed the "trick" which started this thread; the failed transfer-only order does affect those armies (they get marked as "used" and cannot be used again this turn), but they didn't do anything (they simply sat where they were).


For completeness' sake, the reason to mark armies as used when their transfer-only (or, attack-only) didn't happen is to prevent a dirty trick. Let's say you're in Northern Canada (Yukon, NW Territories and Nunavut) and you're attacking southward (British Columbia and Alberta), with these orders:

• Yukon attacks BC (with all armies)
  
• Nunavut attacks Alberta (with all armies)
  
• NW Territories performs an attack-only against BC (with 50% of its armies)
  
• NW Territories attacks Alberta (with all remaining armies)
  

It is our job as players to predict whether our opponent will try to defend both territories or just the one they consider most important. If the 50% armies from the first NW Territories attack are not marked as used, we can be lazy and enter a strategy that works equally well whether the opponent tries to defend both of them (NW Territories attacks both of them), or sacrifices BC in an attempt to at least keep Alberta (the sacrifice is probably in vain; NW Territories attacks with all its armies, knowing that BC has already fallen).

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however you can also do them in games without multi attack for your entertainment

Delay orders need to be (at least) one army to actually delay anything, and they can indeed be used in all game types... and even earn you three achievements:
"Issue at least X orders of one army each, to delay a later attack (last attack must be 10+)"

Edited 6/10/2015 14:59:35

Best results you get by combining both technics 
(transfer only a fix number of armies to your enemy and transfer to own territory by percentage),
as this allows you to react to your enemies actions (attc or not) by changing the size of your blockade.
This already is possible without the transfer only, but not nearly as good as combining both
allows you to adjust the size of the blockade to any integer z1 in [f,d] in case your enemy didnt attc and 
any integer z2 in [1,z1] in case he did attc (you choose both integers as you want them, and with 
the correct f and p the blockade will be as big as you wanted it in both cases)

with

z1:= #armies you want to blockade if your enemy did not attc
z2:= #armies you want to bloackde if your enemy did attc
a := #attcers (enemy) in case he attcs
d := #defenders(yours)
f := #armies you "transfer only" to your enemy
p := (%armies you transfer away)/100

you do know z1,z2,a,d (well, maybe you miss a by one or two armies, that wont hurt much)
but you do not know f and p (which we want to calculate so we can do the correct orders)
First you may wonder how to chose a integer in [f,d] without knowind d,
but there is nothing to worry, just chose one in [0,d],
it will automatically be capped at f (one term in the following calcualtion is capped at 0 in WL,
but not in my calculation)


obviously

I    z1= d-p*(d-f-1)
II   z2= d-0.6a-p*(d-0.6a-f-1)

solve II for p => p=(z2+0.6a-d)/(-d+0.6a+f+1)

put that into I => z1= d-((z2+0.6a-d)/(-d+0.6a+f+1))*(d-f-1)

solve for f => f = (a (3 z1-3)+(5-5 d) z1+(5 d-5) z2)/(3 a-5 z1+5 z2) 

(a few things should be =/= 0 here, so this is a defined term, we dont care for that)

so now with f we can calulate p (p and f were what we searched for) and we can now make the orders in a way that will result in what we wanted.

of course p and f most likly wont be integers, deal with it (round them)

Edited 6/11/2015 14:27:45

Warlight : the most competitive online math game .

genghis, math can be used everywhere, if you're apt minded to apply it...

ehh how many times I was in a situation when I needed to do this exact thing: attack or just move all my units except "x"

It can be used to attack adjacent territory and leave certain amount of units in place as well. Very smart Timi!

thank you rvw, I did not get the previous explanation, but understood yours

wow！a fantastic trick of blockade.I'll try this next time.

Edited 6/13/2015 10:33:51