从古到今，人们都没有和外星人打过一次仗，可是这一次确实发生了一场战争。
From ancient times to the present, people have never had a war with aliens, but this time there was a war.
事情的起因是这样的：和我们人类发生战争是A星球。某一天，我军在地球表层发现了一个奇怪的飞行器，里面载有外星人。那里面的外星人是A星球的总统，当时人类并不知道，以为那是来攻击我们的飞船，所以我军就用液体能量炮攻击飞行器，将其炸毁。A星球人得知消息后，他们非常生气，很快给我们发来战书，内容如下：
The reason for this is that it's planet a that has a war with us. One day, our army found a strange aircraft on the surface of the earth, which contained aliens. The alien inside was the president of planet A. at that time, people didn't know it. They thought it was to attack our spaceship, so our army used liquid energy guns to attack the spaceship and blow it up. After receiving the news, people on planet a were very angry and sent us a letter of war, which read as follows:
地球人：
Earthlings:
你们炸死了我们总统，我们现在要向你们发起进攻，毁掉你们星球，为总统报仇！在二十九世纪五月十一日，我们将会来一次灭绝性的战争。你们等着瞧吧！
You have killed our president. Now we are going to attack you, destroy your planet and avenge the president! On May 11, the 29th century, we will have an extinction war. You wait and see!
A星球军事部
Military Department of planet a
人类收到战书后，都非常着急，连忙召开联合国紧急会议，各国首脑会聚一堂，大家一致表态：要为保卫地球而战。联合国决定在我国安徽黄山最高峰安装一个CDA号炮弹，并在北京天安门广场前安装一个SSS定时导弹。地球几乎每个地方都作好了作战的准备。
After receiving the letter of war, all human beings were very anxious. They hurriedly convened an emergency meeting of the United Nations. The heads of state gathered together and all agreed to fight for the protection of the earth. The United Nations decided to install a CDA shell at the peak of Huangshan Mountain in Anhui Province and an SSS time missile in front of Tiananmen Square in Beijing. Almost every part of the earth is ready for war.
那一天终于来临了。我们双方都准备好了，他们采取的是分组战法，而我们人类使用的是集体战法。我们有一个总开关，只要一按安钮，炮弹就会受控制自动发射到指定目标。第一回合，我们就将他们派来的飞船给炸了，如果按这个战法打下去，我们一定会赢的。我们又派出去几组空军站队攻击，把雷射炮的杀伤力调到最大，直接进攻他们的主控制系统。可是我们伤亡也不轻，地面上房倒屋塌，一片凌乱。他们看我们的火力这么强，终于使用了终极迫击炮，我们赶紧使用终极武器：巨大空气炮，我们的武器在宇宙中相撞，将他们的迫击炮弹了回去，他们被迫投降，离开了地球，并承诺：永不攻击地球！
That day finally came. We are both ready. They are fighting in groups, and we humans are fighting in groups. We have a master switch. As soon as we press the button, the shells will be automatically launched to the designated target. In the first round, we'll blow up the airship they sent us. If we fight in this way, we'll win. We also sent out several groups of air force stations to attack, to maximize the lethality of laser guns, and directly attack their main control system. But our casualties were not light. The houses on the ground collapsed and were in disorder. They saw that our firepower was so strong that they finally used the ultimate mortar. We hurriedly used the ultimate weapon: the huge air cannon. Our weapons collided in the universe and returned their mortar shells. They were forced to surrender and leave the earth. They promised: never attack the earth!
我们人类保卫战终于胜利了！
We finally won the human defense!