Soldiers are one of the most overlooked tribal decks in the Magic: The Gathering card game. Soldiers are a very common creature type from the early days of Magic: The Gathering to today. However, the soldier creature type has changed drastically in modern sets. Modern sets are those with the more modern boarder around them. The first modern set was Mirrodin. In this set they started using the human creature type, which made soldiers become a secondary creature type. Now soldiers come as an addition to human or other creature types, but there are many cards that will pump soldier creatures from past sets.
The best thing to do when putting together a soldier deck is to go to your local card shop that sells used cards and go through their bargain boxes of commons and uncommons. There should be several old cards in that box, and if you dig around you will find some very interesting soldier cards with great abilities that compliment each other. Most of these cards will be white, but some of them will be red, you may decide that you might be tempted to make your deck multiple colors, and this is not a bad choice. There are some soldier cards that even allow you to play them using either red or white mana, like Goblin Recruit. This can help you with the mana problems that always come up when you deal with more then one color. To be safer about your mana supply you might want to stick solely with white, as the best soldier cards are mostly white.
Once you have picked out your cards you will probably notice that many of them have first strike or vigilance. These abilities are very handy, as having first strike can save your creatures life from any other creature that does not have first strike, but has toughness low enough for your creature to kill. Vigilance is another great ability as it allows your creatures to attack without tapping allowing them to block during your opponents attack phase. Meaning your creatures will pull double duty.
Newer cards also have great abilities, and you may wish to combine your creature type with another creature type. For instance if you add creatures that are soldiers that also help humans, you can use the old soldier cards, in addition with the new ones creating a better deck.
Remember when you construct your deck; you will have to play it a few times in order to tune it correctly. You will probably not have a good deck your first time.