REPORT OF CAPT. GEORGE B. M-'CLELLAN. 289 



paces from their detacliments, and ought to regulate their intervals so as never to lose sight of 

 ■aach other, and to form a continuous chain around the head and flanks of the main advanced 

 guard. 



§ 15. The general arrangement, without regard to the ground, of an advanced guard, com- 

 posed of 10 companies of cavalry, and 6 pieces of horse artillery, is shown in Plate I. 



§ 16. An advanced guard during a march in retreat consists of a small numher of troops, 

 (isually determined as in time of peace. 



Its purpose is : 



1. To open the way for the main body, and remove all obstacles from the road. 



2. To serve as the escort of the train, which should move, at least, as far in advance of the 

 main body as it does in rear of it during an offensive march. 



§ 17. In this case, the advanced guard sends out front and flank detachments and patrols, 

 ^vhich are arranged precisely as in offensive marches. Here the principal object to be kept in 

 view is that all the detachments may be promptly united at any moment. 



§ 18. During an offensive march the rear guard is formed according to the same principles as 

 in advanced guard during a retreat. Its duty is as follows : 



1. To watch over the preservation of order in the rear of the column. 



2. To pick up stragglers. 



3. To protect the rear of the column and the train against sudden attacks by parties of the 

 onemy. 



§ 19. In a retreat, it is the duty of the rear guard to cover the movements of the main body, 

 as well as to repiilse and delay the enemy in every possible manner. In this case, its duty 

 becomes as difficult as that of the advanced guard in an offensive march, and sometimes more 

 ;^o, especially when the retreat is effected in sight of the enemy. The rear guard must, at every 

 favorable point, use all means to check the enemy, and thus render it possible for the main 

 body to retreat without precipitation. To efiect this, it should always be much more indepen- 

 dent than the advanced guard in offensive marches, for the latter can always retreat upon the 

 main body, or be readily supported by it. 



§ 20. With regard to the safety of the main body, the rear guard in a retreat observes the 

 rules laid down in numbers 1, 2, and 5, of § 10. 



§ 21. The strength of the rear guard depends upon several circumstances : 



1. Upon our own and the enemy's designs. 



2. Upon the proximity of the enemy. 



3. Upon the nature of his operations. 



4. Upon the distance from the main body, and the order of march of the latter. 



If the enemy pursues vigorously, or if the main body ought to fall back a great distance 

 behind the rear guard, then the latter should be strong enough to operate independently, and 

 defend itself obstinately in all favorable positions. Such a rear guard should be one-fifth, or 

 even one-third of the whole force. 



§ 22. The rear guard should cover its movements, both in the offensive and retreat, in the 

 manner laid down for the advanced guard in §§ 12, 13, and 14. 



§ 23. If the main body marches in several columns, all the rear guards should communicate 

 with each other by means of patrols. They ought also to move in line — that is to say, on the 

 same general line perpendicular to the general direction of the march. 



§ 24. To the advanced guard in all cases, and to the rear guard in retreat, mounted engineer 

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