Jīng / guò / cháng / qī / xùn / liàn / tā / men / zhú / jiàn / chéng / wéi / yì / zhī / néng / dǎ / yìng / zhàng / de / tiě / jūn

经过长期训练，他们逐渐成为一支能打硬仗的铁军。

After prolonged training, they gradually became a force capable of winning tough battles.