The German attacks in 1918
The first German attack, Operation "Michael"/Somme Offensive (21 March -5 April), was by far the largest of the assaults. At the onset of the attack, the German 17th, 2nd and 18th Armies contained 76 divisions, of which 39 were in the front line, 22 in the second echelon, and 15 in the third (reserve) echelon. Of the 76, 56 divisions were dubbed "Stoss" or attack units (fur den Angriff bes. ausgestattete und ausgebildete Divisionen). During the course of the attack 3 additional divisions (of the original 76) were designated as Stoss units. By the end of the attack, 17 additional divisions had been fed into the battle. Of these, perhaps 4 or 5 were Stoss. The Michael attack was supported by 6,608 guns, 3,534 minenwerfer, and 1,070 aircraft.
The second "Lys" drive (9-29 April) was a far smaller affair. On 9 April the attack zones of the 4th and 6th Armies contained 26 divisions (14, 5, 7 in the three echelons) of which only 12 were attack divisions. During the operation at least 14 additional divisions were engaged, about 7 of the Stoss and at least 5 of them divisions that had fought in the previous Somme attack. I don't have figures handy for the support elements.
The third "Aisne" offensive (27 May -6 June) was originally intended to be a diversionary effort to draw French and British reserves away from Flanders where Ludendorff hoped to renew the assault on an enlarged scale. But the unexpected attack of this "Angriff des Chemin des Dames" derailed this plan. The German 7th and parts the 1st and 18th Armies had 39 divisions available (distributed 23, 5, 11 by echelon). Of these 21 were Stoss, almost all veterans of the previous Somme attack. At least 6 additional divisions were fed into the attack. Support included 5,263 guns, 1,233 MW., 3,080 gas projectors, and 500 planes.
The fourth "Matz" attack (9-13 June) was a relatively limited operation designed to round-out the Somme and Aisne-Marne salients created by the previous attacks. In this its 27 divisions, of which only some 7 were (depleted) attack units, it did not succeed.
The fifth and final drive on either side of Rhiems (15-17 July) was also intended to round-out the line and pin down Allied reserves as a preliminary to a resumption of the Flanders attack. The 1st and parts the 7th and 3rd Armies had 50 divisions available, 29 in line (of which two were exempted from the attack) and 21 in their rear. At least 30 of these divisions were ostensible Stoss formations, although that designation seems to have meant relatively little by this time. Most were veterans of prior attacks. The offensive was supported by 6,353 guns, 2,200 MW and some 900 planes.
The primary source for the above is Vol XIV of the German official history, _Der Weltkrieg_, Beilage 38.