4 sentences

1. 永乐时期，明朝的国力达到了鼎盛。

   Yǒng​lè shí​qī, Míng​cháo de guó​lì dá​dào le dǐng​shèng.

   During the Yongle period, the power of the Ming Dynasty reached its peak.

   Source: Dong Chinese Dictionary

2. 改革开放增强了我国的综合国力。

   gǎi​gé kāi​fàng zēng​qiáng le wǒ guó de zōng​hé guó​lì.

   Reform and opening up have strengthened our country's comprehensive national power.

   Source: Dong Chinese Dictionary

3. 维多利亚女王在位期间，英国国力达到了顶峰。

   Wéi​duō​lì​yà nǚ​wáng zài​wèi qī​jiān, Yīng​guó guó​lì dá​dào le dǐng​fēng.

   During Queen Victoria's reign, British national power reached its peak.

   Source: Dong Chinese Dictionary

4. 那个朝代因为连年的大兵，国力逐渐变得衰弱。

   nà​ge cháo​dài yīn​wèi lián​nián de dà​bīng, guó​lì zhú​jiàn biàn de shuāi​ruò.

   Due to years of constant warfare, that dynasty's national strength gradually weakened.

   Source: Dong Chinese Dictionary