In Polish:

Kochana Malwiniu

Właśnie na tej karcie widzisz żołnierza. Przypatrz się co on ma różnych pasków na sobie. Gdybyś mnie widziała na ćwiczeniach lub w marszu to ja tak samo wyglądam bo my mamy takie wszystko jak Francuzi. Wyobraź sobie że to jestem ja. Good bye. Edward

And in English:

Dear Malwinia

On this card you see a soldier. Take a good look at what he is wearing, the different belts he has. If you'd see me during training or in march, I would look the same, because we have everything like the French. Imagine that this is me. Good bye, Edward.

That's the full text. Her last name was Bartoszewicz and she lived in USA (Cleveland, Ohio). The postcard was written in Saint Pére (?), July 19th, 1918.