For example, how did losses of company commanders differ between say German and British armies?

For the US Army you can find data on officer casualties by rank in Attrition pp. 61-62 (see our order page if you would like a copy). In summary, officer casaulties as a percent of total casualties by war in the 20th century were:

WW I 6.6
WW II 10.4
WW II (less USAAF) 6.1
Korean War 5.0
Vietnam (killed only) 10.9

The battle casualtry loss rate by rank for the US Army in World War II was:

General Officer and all field grades 35
Captain 53
1st Lieutenant 105
2nd Lieutenant 204
Warrant Officer 8

Officer casaulties in the US Army as a percentage of their strength in each branch was:

Infantry 25.7
Armor & Mechanized Cavalry 17
Field Artillery & Chemical 8.5
Medical Corps 0.9
Engineers 2.8
AAA & Coast Artillery 1.1
Other 3.6
USAAF 3.6

First, from Eighth Army in North Africa we can extract the following from the casualty summary report completed 3 May 1944 (“Libyan Casualties – Part III, WO 201/2834). Note that only the British losses were calculated by arm, Commonwealth, Colonial and Allied losses were given as national totals only.

2-12 Jul 1942: 109 of 2965 O (officers) were casualties (2.7%), 1004 of 77808 OR (other ranks) were casualties (1.3%), O casualties were 9.8% of the total. Highest casualties were in RA Field and AT Rgts, where O losses were 8.6%, second highest was RAC with 5%.

30 Aug-6 Sep 42: 112 of 3721 O casualties (3%), 1409 of 72176 OR casualties (2%), O casualties were 7.4% of the total. Highest casualties were in Infantry, where O losses were 9.6%, second highest was RAC with 4.9%.

23 Oct-4 Nov 42: 762 of 6850 O casualties (11.1%), 8282 of 130995 OR casualties (6.3%), O casualties were 8.4% of the total. Highest casualties were in Infantry and RAC, both with O losses of 21.7%, second highest was RE with 12%.

Overall, for the period 2 July 1942 to 14 May 1943, the average loss rate for officers varied from 1 to 11 percent, for OR it was 0.4 to 6.4 percent.

Additional information may be derived from ORS Report No. 19 “Infantry Battle Casualties,” by No. 2 AORG. That report looked at the loss patterns of infantry battalion officers in 7 divisions in NW Europe between 6 June and 6 November 1944 (3, 15, 43, 49, 50, 51, and 53 ID). It was found that of 2407 casualties the loss rates by position were (total battle casualties/total KIA – when known):

I can give you the losses of the Rumanian Army in W.W. 2:

DEAD

Officers NCOs Rank&File
------------------------------
3972 2599 86049

WOUNDED & SICK

Officers NCOs Rank&File
------------------------------
11648 8067 314251

MIA

Officers NCOs Rank&File
------------------------------
22592 17460 354210

TOTAL

Officers NCOs Rank&File
---------------------------------------
22592 (2.8%) 17460 (2.2%) 754510 (95%)

I hope this helps.

BY POSITION:
Army Group Commanders killed was 1
Army Commanders killed was 3
Corps Commanders killed was 30
Division Commanders killed was 134
Total is 168

BY RANK:
Generalfeldmarschall killed is 1 [5 stars]
Generaloberst killed is 1 [4 stars]
General der [Inf. or Art. or Panzer etc.] killed is 25 [3 stars]
Generalleutnant killed is 67 [2 stars]
Generalmajor killed is 74 [1 star]
Total is 168

BY COMMAND DURATION:
one month or less is 31 killed
two to five months is 37 killed
six to nine months is 38 killed
ten to twelve months is 26 killed
more than twelve months is 36 killed
Total is 168

There is also a listing of the total number of General officers lost in the war as follows:
killed in action is 168
died of wounds is 55
accidental deaths is 30
suicides is 64
executed by Germans is 20
executed by Allies after the war is 33
died as a POW in a camp is 128
died of health problems not associated with the war is 145
missing in action is 32
Total is 675

When you compare the killed numbers [675] to the total number of officers that achieved each rank [2,344] then 28.8% of all German General officers died from all causes. I doubt that any other country approached these figures.

BREAKDOWN BY RANK:
Generalfeldmarschall rank attained by 19 officers
Generaloberst rank attained by 38 officers
General rank attained by 334 officers
Generalleutnant rank attained by 795 officers
Generalmajor rank attained by 1,158 officers
Total of 2,344 individuals attained a General officer rank during World War II

Another interesting section covers the types and areas of wound locations as follows:
The German Medical Units studied 3,015,589 wounded soldiers finding that 24% were killed in action, 30% were seriously wounded and 46% were lightly wounded.

In 1942 the wound locations were as follows:
5% were to the skull
8% were to the facial area
1.3% were to the throat area
6.3% were to the shoulder
7.3% were to the chest
6.3% were to the upper arm
16.5% were to the lower arm
3.5% were to the stomach
10.1% were to the upper leg
28.3% were to the lower leg
3.4% were to the back

By 1944 the fatal wound locations were as follows:
head is 42.61%
chest is 22.11%
stomach is 7.95%
back is 4.11%
throat is 3.36%
legs is 3.04%
arms is 0.64%

Cold weather injuries through December 1941 in the front aganist Moscow were over 112,000 with 14,000 classified as major requiring one or more amputations, 62,000 as moderate not requiring any amputations but resulting in total incapacitity and 36,000 classified as light meaning the soldier was able to return to action in 10 days or less. The German soldiers referred to the Eastern Front Medal as the Gefrierfleisch Orden-Order of the Frozen Meat.

Some of the causes of the death of General officers is:
air attack is 20 killed
artillery is 12 killed
small arms fire is 11 killed
minefield killed is 9
partisians is 7 killed
anti-tank fire is 6 killed
tank fire is 5 killed

I recomend this book to those interested in the subject. Lots of information on each individual killed.

Ron