The thesis is the essence of an argumentative essay. In a single, clear sentence, it sums up what point you are trying to make. The thesis statement should assert a position on a particular issue -- one that a reader can potentially argue against. Therefore, the thesis cannot be a fact. For example, if a professor assigns the general topic of war, you can formulate the following thesis statement: "The United Nations must be redesigned because it is currently incapable of preventing wars." The rest of your essay serves to explain and provide evidence in support of your thesis statement.
Introductions can be tricky. Because the introduction is the first portion of your essay that the reader encounters, the stakes are fairly high for your introduction to be successful. A good introduction presents a broad overview of your topic and your thesis, and should convince the reader that it is worth their time to actually read the rest of your essay. Below are some tips that will make writing an introduction a little less daunting, and help us all to write essays that don’t make our professors want to bang their heads against the wall.
The attention grabber you use is up to you, but here are some ideas: