Bootstrap card desk how to line them up horizontally?

Question

css

Hello, sorry for the possibly stupid question, but still ...
I'm trying to line up the card desk horizontally, but for some reason the browser lines them up vertically

<div class="container">

    <div class="col-md-12">

        <div class="card-deck-wrapper">
            <div class="card-deck">
                <div class="card">
                    <img class="card-img-top" src="/images/d_c.jpg" alt="Card image cap">

                    <div class="card-block">
                        <h4 class="card-title">Card title</h4>

                        <p class="card-text">This is a longer card with supporting text below as a natural lead-in to
                            additional content. This content is a little bit longer.</p>

                        <p class="card-text">
                            <small class="text-muted">Last updated 3 mins ago</small>
                        </p>
                    </div>
                </div>

                <div class="card">
                    <img class="card-img-top" src="/images/d_c.jpg" alt="Card image cap">

                    <div class="card-block">
                        <h4 class="card-title">Card title</h4>

                        <p class="card-text">This is a longer card with supporting text below as a natural lead-in to
                            additional content. This content is a little bit longer.</p>

                        <p class="card-text">
                            <small class="text-muted">Last updated 3 mins ago</small>
                        </p>
                    </div>
                </div>

            </div>
        </div>

    </div>

</div>

Answer 1

<div class="container">
 <div class="row">
  <div class="col-md-6">
   <div class="card-deck-wrapper">
   </div>
  </div>
  <div class="col-md-6">
   <div class="card-deck-wrapper">
   </div>
  </div>
 </div>
</div>