In Herman Cron's book in the German army, in 1914 the 8th army, at the start of the war is listed with 5 corps+assorted divisions and brigades. What happened to these troops as the year went on? During the Masurian lakes the 8th only had 6 corps, two of which came from the western front. Later on, this discrepancy remains. Any clues? What about the Worysch detachment? What that formed from 8th Army troops?

The 8th Army consisted of only 4 Corps, 1 division and some smaller units, as the 'Landwehr' Corps Col.-Gen. von Woyrsch was associated with Gen. Dankl's Austrian I. Army...The 2 Corps from the West arrived for the battle of the Masurian lakes, thus making 6 Corps (not counting sole divisions and brigades).

I think that Cron has added that Corps in the first, but not on the second description (this would at least fit )

What do you mean with 'the discrepancy remains'? the 8th gave up a lot of troops in mid-september to the new 9th army, maybe you should have alook at it.

The 9th army units are accounted for. The Woyrsch detachment was a German unit filled with the 1st Landwehr corps, a unit Cron assigned to the 8th army. Woyrsch was called back to the colors in January 1914, which means that the assignment of the Landwehr corps and 3 additional divisions (something my additional research has turned up) happened sometime between the start of the war and Tannenberg.

The 8th Army initilly consisted of 5 Corps, as you already said:

I., XX., XVII. Army Corps, I. Reserve Corps, and the 'Landwehr' Corps Woyrsch
additionally it had the 3rd Reserve division, the 1st cavalry division, the 'Landwehr' Division von der Goltz (from Sleswig arriving during August), and several Ersatz troops.
The Landwehr Corps Woyrsh is counted into your first list.

What I tried to suppose (I'm sorry If i didn't get it over clear enough as i am german not english), was that, as the Corps Woyrsh was assigned under the orders of the I. Austrian Army in Poland in mid-August.
BUT, as it was in Poland, not in East Prussia, i think that Mr. Cron did not count it into the troops actually fighting at the Masurian lakes, which were the other above mentioned plus the Guard Reserve Corps, XI. Army Corps and 8th cavalry division.
-> 6 Corps actually fighting at Masurian lakes.

do you agree?

SMSkaiser, it seems that you are right. Congrats on your english skill. My German is no where as good. There are not enough english language resources on the subject; could you suggest any in German? Thanks again