Unit upgrades

Overview
Upgrading or leveling up your units enables you to train the rookies you start with into battle-hardened veterans. You need to have the required amount of resources: experience and money. Apart from experience and money you also need an increasing amount of oil when upgrading once in every 20 levels.

Each unit rank has its maximum available level. When you want to upgrade units above their current maximum level you need to promote them to a higher rank. This process is called Promoting. In order to promote units you need to merge several (2-3) lower rank units of the same nation.

Required units
There is a varying number of lower rank units needed when promoting. The important point is that you can only use units of the same nation so for example, you cannot promote American units using British units. Sometimes, any units of the same nation can be used and from time to time, you need to use the same unit as the one that you want to promote. In order to reach as high as to the supreme level you need to gather and use 8 epic cards of the same unit (2 are used to promote to epic+, 2 more for legendary+ and additional 4 are needed for the supreme level) and 20 additional epic cards of different units of the same nation, as you can see from the table below - 1 supreme unit requires 28 epic units altogether.

The amount is shown in the following figure, e. g. you need 2 epic units to get 1 promoted epic+ unit and these 2 epic units equal (were created using) either 6 rare+ units (each epic unit requires 3 rare+ units to get promoted) or 18 rare units (each rare+ unit requires 3 rare units to get promoted). So for example in order to reach as high as to the supreme level you need to obtain and use 252 basic rare units which equals to 28 epic units. Also note that common units cannot be promoted. They can be exchanged for Gears which can be used for purchases in the in-game shop.

Unit ranks
The following unit ranks are available:

Equipment
The unit power can be substantially improved by purchasing and using additional equipment. There are 4 equipment slots usable by each unit, their types differ for each unit type. There are equipment ranks, the higher the rank the more powerful and also more expensive the equipment piece is. Equipment can be upgraded using other equipment pieces. New equipment can be either created in the Arsenal or purchased in the In-game shop.