XL] THE RACES OF THE DANUBE. 205 



undo the costly work which this has accomplished. 

 Though the enemy has at times appeared in the 

 shape of unmitigated tribal barbarism as in the 

 invasion of Huns in the fifth century and of Mongols 

 in the thirteenth and at other times in the shape of 

 an inferior type of civilisation, as exemplified by the 

 Arabs and Turks, the principle involved has always 

 been the same. In every case the stake has been the 

 continuance of the higher civilisation, though the 

 amount of risk has greatly varied, and in recent 

 centuries has come to be very slight. At the present 

 day the military strength of mankind is almost 

 entirely monopolised by the higher civilisation, and 

 it is no longer in danger of being overwhelmed by 

 external violence. But when the Greeks confronted 

 a social organisation of inferior type at Marathon and 

 at Salamis, the danger was considerable ; and in pre- 

 historic times it may well have happened more than 

 once that some germ of a progressive polity has been 

 swept away in a torrent of conquering barbarism. 



Until the rise of the Roman power the chief mili- 

 tary business of the cultivated community had been 

 to drive off the barbarian, to slaughter him, or reduce 

 him to slavery ; but the more profound policy of 

 Rome transformed him, whenever it was possible, 

 into a citizen, and enlisted his fighting power on the 



