These Macedonians, unable to take the field against so numerous an invader, shut themselves up in such strong places and fortresses as the country possessed. Of these there was no great number, most of those now found in the country having been erected subsequently by Archelaus, the son of Perdiccas, on his accession, who also cut straight roads, and otherwise put the kingdom on a better footing as regards horses, heavy infantry, and other war material than had been done by all the eight kings that preceded him. Advancing from Doberus, the Thracian host first invaded what had been once Philip's government, and took Idomene by assault, Gortynia, Atalanta, and some other places by negotiation, these last coming over for love of Philip's son, Amyntas, then with Sitalces. Laying siege to Europus, and failing to take it, he next advanced into the rest of Macedonia to the left of Pella and Cyrrhus, not proceeding beyond this into Bottia and Pieria, but staying to lay waste Mygdonia, Crestonia, and Anthemus. The Macedonians never even thought of meeting him with infantry; but the Thracian host was, as opportunity offered, attacked by handfuls of their horse, which had been reinforced from their allies in the interior. Armed with cuirasses, and excellent horsemen, wherever these charged they overthrew all before them, but ran considerable risk in entangling themselves in the masses of the enemy, and so finally desisted from these efforts, deciding that they were not strong enough to venture against numbers so superior.