The forward youth that would appear
Must now forsake his Muses dear,
Nor in the shadows sing
His numbers languishing.
'Tis time to leave the books in dust,
And oil th' unused armour's rust,
Removing from the wall
The corslet of the hall.
So restless Cromwell could not cease
In the inglorious arts of peace,
But through advent'rous war
Yet again Marvell is building up the sense of degradation of the normal state of life in the 1600s before the first English Civil War. 
 A corslet is a piece of armour that at the time was worn by the average soldier.
An Horatian Ode Upon Cromwells Return from Ireland