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Commanded by Major General Samuel P. Heintzelman
Defences North of the Potomac Lieutenant Colonel J. A. Haskins  
First Brigade Colonel A. A. Gibson  
Second Brigade Colonel Lewis O. Morris  
Third Brigade Colonel W. R. Pease (to 4/14)
Colonel A. Piper
Defences South of the Potomac

Brigadier General Robert O. Tyler (4/15- 4/26)
Colonel T. R. Tannatt

First Brigade Colonel T. R. Tannatt org. 4/15 from Art. Alexandria (below)
Second Brigade Colonel G. D. Wells org. 4/15 from Art. S. of Potomac (below)
Abercrombie’s Division Brigadier General J. J. Abercrombie  
First Brigade Colonel Francis Fessenden (after 4/17) from Casey’s Div., 4/17 (below)
Second Brigade Colonel B. Porter (to 4/17)
Brigadier General George J. Stannard

to Dept. Va.; replaced by 2nd Brig.
from Casey’s Div., 4/17 (below)

Third Brigade Colonel William Gurney
Brigadier General Alexander Hays

to Dept. Va.; replaced by 3rd Brig.
from Casey’s Div., 4/17 (below)

Casey’s Division Major General Silas Casey  
First Brigade Colonel Francis Fessenden to 1 Brig. Abercrombie’s Division (above)
Second Brigade Brigadier General Edwin H. Stoughton to 2 Brig.  Abercrombie’s Division (above)
Third Brigade Brigadier General Alexander Hays to 3 Brig. Abercrombie’s Division (above)
Pennsylvania Reserves Division Colonel H. G. Sickel  
First Brigade Colonel William McCandless (to 3/29)
Colonel William Sinclair
Second Brigade Colonel H. C. Bollinger to District of Alexandria (below)
Third Brigade Colonel J. W. Fisher  
Cavalry Division Major General Julius Shahel  
First Brigade Brigadier General J. T. Copeland  
Second Brigade Colonel R. Butler Price  
Third Brigade Lieutenant Colonel R. Johnston (to 4/9)
Colonel O. DeForest
Jewett’s Independent Brigade Colonel A. B. Jewett  
23rd Maine Infantry Regiment Colonel William W. Virgin  
39th Massachusetts Infantry Regiment Colonel P. Stearns Davis  
14th New Hampshire Infantry Regiment Colonel Robert Wilson  
10th Vermont Infantry Regiment Colonel Albert B. Jewett  
11th New York Cavalry, Cos. E, F & I    
10th Massachusetts Independent Battery    
District of Washington Brigadier General J. H. Martindale  
2nd District of Columbia Infantry Regiment Colonel Charles M. Alexander  
10th New Jersey Infantry Regiment Colonel William R. Murphy to 7th Corps, 1st Div., 3rd Brig.
118th New York Infantry Regiment   to 7th Corps, 1st Div., Reserve Brig.
152nd New York Infantry Regiment   to 7th Corps, 1st Div., 1st Brig.
169th New York Infantry Regiment   to 7th Corps, 1st Div., 2nd Brig.
27th Pennsylvania Infantry, Co. F    
150th Pennsylvania Infantry, Co. K    
157th Pennsylvania Infantry (4 cos.)    
District of Alexandria Brigadier General John P. Slough  
1st District of Columbia Infantry Regiment    
26th Michigan Infantry Regiment   to 7th Corps, 1st Div., 1st Brig.
153rd New York Infantry Regiment    
11th Rhode Island Infantry Regiment Colonel George E. Church  
Artillery, Distict of Alexandria Brigadier General Robert O. Tyler  
1st Connecticut Heavy Artillery Colonel Henry L. Abbott  
19th Connecticut Infantry (Hv. Artillery) Colonel Leverette Wessells  
Artillery Brigade South of the Potomac Colonel M. Cogswell  
1st Massachusetts Heavy Artillery    
34th Massachusetts Infantry Regiment Colonel George D. Wells  
2nd New York Heavy Artillery    
3rd New York Heavy Artillery Battalion    
1st Wisconsin Heavy Artillery    
Light Artillery Camp Camp Berry Brigadier General William F. Berry  
1st Delaware Battery    
1st Michigan Artillery, Battery I   to Cav. Div. (above)
1st Michigan Artillery, Battery K    
1st New York Artillery, Battery A    
12th New York Independent Battery    
16th New York Independent Battery    
19th New York Independent Battery    
27th New York Independent Battery    
1st West Virginia Artillery, Battery A    
Pennsylvania Independent Battery H