From the point of view of strategy--that is, the conduct of the great operations of a campaign--Osman's defence of Plevna yields lessons of equal interest. It affords the most brilliant example in modern warfare of the power of a force strongly intrenched in a favourable position to "contain," that is, to hold or hold back, a greater force of the enemy. Other examples are the Austrian defence of Mantua in 1796-97, which hindered the young Bonaparte's invasion of the Hapsburg States; Bazaine's defence of Metz in 1870; and Sir George White's defence of Ladysmith against the Boers. We have no space in which to compare these cases, in which the conditions varied so greatly. Suffice it to say that Mantua and Plevna were the most effective instances, largely because those strongholds lay near the most natural and easy line of advance for the invaders. Metz and Ladysmith possessed fewer advantages in this respect; and, considering the strength of the fortress and the size and quality of his army, Bazaine's conduct at Metz must rank as the weakest on record; for his 180,000 troops "contained" scarcely more than their own numbers of Germans. On the other hand, Osman's force brought three times its number of Russians to a halt for five months before hastily constructed lines. In the opinion of many authorities the Russians did wrong in making the whole campaign depend on Plevna. When it was clear that Osman would cling to the defensive, they might with safety have secretly detached part of the besieging force to help the army of the Czarewitch to drive back the Turks on Shumla. This would have involved no great risk; for the Russians occupied the inner lines of what was, roughly speaking, a triangle, resting on the Shipka Pass, the River Lom, and Plevna as its extreme points. Having the advantage of the inner position, they could quickly have moved part of their force at Plevna, battered in the Turkish defence on the Lom, and probably captured the Slievno passes. In that case they would have cleared a new line of advance to Constantinople farther to the east, and made the possession of Plevna of little worth. Its value always lay in its nearness to their main line of advance, but they were not tied to that line. It is safe to say that, if Moltke had directed their operations, he would have devised some better plan than that of hammering away at the redoubts of Plevna. In fact, the Russians made three great blunders: first, in neglecting to occupy Plevna betimes; second, in underrating Osman's powers of defence; third, in concentrating all their might on what was a very strong, but not an essential, point of the campaign.